Hence, by using the also operator, the code can be modified as: This way we can execute the intermediate result within the execution chain without breaking the chain, thereby leading to a better readable code. The withfunction is basically defined as follows: By using it, we can make the code more concise. Your code block might need to reference the existing this scope. Because the scope functions are all quite similar in nature, it's important to understand the differences between them. The difference is run refers to the context of the object as “this” and not “it”. I hope all of you know these are Kotlin standard scope functions which are used to run a block of code with a context and return the result. COVID-19 - data, chart, information & news. ... Kotlin™ is protected under the Kotlin Foundation and licensed under the Apache 2 license. Functions in Kotlin are very important and it's much fun () to use them. Supported and developed by JetBrains. Build final native binaries. Let's assume Apply is a person name, I can make a grammatically correct English sentence with them: it also let Apply run. Not clear still right? And hence, to correct this, we need to change the code as: So performing a null check using a “with” operator is difficult and this is where we can replace it with “run” as follows: The apply function is similar to the run functionality only in terms of referring to the context of the object as “this” and not “it” and also in providing null safety checks: Specifically for Android Development, "apply" can be useful in many cases. Here’s how you’d include the latest version of Kotlin in your project-level build.gradle file: Are we using them correctly? Let's start with a simple requirement. The also, apply, let, run, and with functions, when used properly in Kotlin, make your code more readable. The “ run ” operator is similar to the “ let ” operator in terms of accepting a return value that is different from the object on which the scope function is being applied to. The advantage of using “also” operator is that while doing a chain of operations, this operator helps in evaluating the current operating value if required. a block of code, in the context of an object. But before going through these examples, let’s consider a Model class “Person”. Intention of Kotlin's "also apply let run with" One of the things that puzzled me when I started with ... Kotlin and Java EE: Part One - From Java to Kotlin. As a starting point for examination, let’s look at some code. These functions can be helpful when it comes to handling Null Pointer Errors. You probably already heard about them and it's also likely that you even used some of them yet. This implies that the “let” operator provides an option to perform an operation on the current object and return any value based on the use case. So let's forget about it also let apply run for a second. Subtle differences between Kotlin's with(), apply(), let(), also(), and run() June 3, 2017 in programming. So what happens if we don’t return anything in the “let” block? 1: Just use […] “the tldr; on Kotlin’s let, apply, also, with and run functions” is published by Andre Perkins in ProAndroidDev. In this guide, we’re going to clarify four of these scope functions in particular - let(), also(), run(), and apply(). Giới thiệu. Nice! It also comes with an efficient way of working with background threads, main threads, and dedicated I/O threads. Let’s say we make the “. Ok, I just made that up. That is the reason we did not use “${this.name}” as it would be redundant here since the block of code understands that “name” is used here concerning the Person object. Let's say you have a pug. TL;DR obj.let{it}, obj.run{this}, with(obj){this} - returns result of last line obj.also{it}, obj.apply{this} - returns the same object. Solution no. We can press the button here or you can select Run and choose Run App in the menu. 暖心芽 (WIP) ️ - reminder of hope, warmth, thoughts and feelings. Hence, a “ run ” operator can be used to initialize an object and return the result of it. Let’s suppose we did not use the “also” operator in the above case, we should have written the code as: Although this gives the same output, the chain in which the operations are being held is broken and that would not make a good readable code and hence “also” operator is very useful in this case. There are five scoped functions in Kotlin: let, run, with, also and apply. This guide will show when and when not to use them. Last update Nov 4, 2019 Understanding Kotlin's let (), also (), run (), and apply () Kotlin’s standard library includes some often-used scope functions that are so abstract that even those who have been programming in Kotlin for a while can have a hard time keeping them straight. Let’s go ahead and turn this by coming up here and selecting the run app. Well, that’s the beauty of kotlin! We will be discussing the following topics in this article: Well, what does this mean? let. Let's say you have a pug. Kotlin let is a scoping function wherein the variables declared inside the expression cannot be used outside. Ok, I just made that up. The second dimension is the return value. Lets-Plot-Kotlin in Datalore notebooks Datalore is an online data science notebook by JetBrains. Let’s consider a case where a Person object can be nullable. Let's assume Apply is a person name, I can make a grammatically correct English sentence with them: it also let Apply run. Let’s take the following example: So our aim is to fetch the values in the ArrayList whose length is greater than 3. Kotlin has many unique language features for someone coming from Java. Thanks to the resemblance, I even tried forming sentence using them. fun returns “Result” — let, run, with when we use the above functions, you can use the object within the block and returns whatever the last line of the block gives as a result. Kotlin is being officially used in Android development, and every Android developers are probably busy picking up Kotlin. So apply() fits in the first category - it returns the receiver object. It refers to the context of the object by using the “it” keyword and hence, this “it” can be renamed to a readable lambda parameter. That includes me. So let’s see the difference between apply and run functions. Although whatever you do with scope functions can be done without, they enable you to structure your code differently. Code written sequentially is typically easier to read, and can even use language features such as exceptions. One point here is that since the context is referred to as “this”, it cannot be renamed to a readable lambda parameter. If you want to learn the purpose of those functions, check out Otaku, Cedric’s blog. Let’s focus on one of these functions,let, in order to write safer code and less boilerplate. The second advantage is it easily helps in providing null checks. and you want to add a horn to it. The “run” operator also helps in easy null checks similar to the “let” operator. So, if “with” is the same as “run”, what’s the difference? Here’s an example of apply(): In this code listing, you’ll notice a few things: These three characteristics actually apply to all four functions, not just apply(). The following demonstrates the four functions, accomplishing the same thing in each case - printing Hello and then returning the length of the string. Run tests. Kotlin’s standard library includes some often-used scope functions that are so abstract that even those who have been programming in Kotlin for a while can have a hard time keeping them straight. Run tests. 1.0. .also () .let () .apply () .run () They are magical because they can perform some Kotlin magics and at the same time greatly resemble English words. pug analogy, part I There's a famous saying "to begin learning is to begin to forget". ... For having additional effects or grouping function calls on an object use let, run, with. Using them can increase readability and make your code more concise. Publish a multiplatform library. Kotlin is being officially used in Android development, and every Android developers are probably busy picking up Kotlin. Hello and Welcome to our MindOrks write up on “Scope Functions in Kotlin”. This can be very helpful if we have nested let blocks, and since all let blocks refer to the context of their respective objects as “it”, it might be difficult for the compiler which objects we are referring to: We Know how lengthy the code would be to perform a null check in Java. The “with” operator is completely similar to the run operator that we just discussed. Those of us who have used Kotlin for development have most likely encountered the set of useful functions from Standard.kt. Native. Let’s see the same example, but this time using also(): This time, since we’re using also() instead of apply(), we had to prefix the set() calls with it. Pixtory App (Alpha) - easily organize photos on your phone into a blog. Kotlin let let takes the object it is invoked upon as the parameter and returns the result of the lambda expression. But with run(), the result returned is the result of the code block, so we’d shuffle that call to get(): These two dimensions - context and result - can form a nice little grid that can make it easy to remember what’s what: Following the first letter of each, you get the acronym “LARA”. This guide will show when and when not to use them. Dealing with optionals. The return value. With the help of these functions ( let , run , with , apply and also ),we can operate on objects within a certain context. Refer Kotlin Android – ImageView Example to create an Android Application with just an ImageView in LinearLayout. How can we make the best use of it? The “also” function is similar to the let functionality only in terms of referring to the context of the object as “it” and not “this” and also in providing null safety checks: Here we can see the usage of the readable lambda parameters, similar to what we have seen in the “let” operator case. Yeah. The also, apply, let, run, and with functions, when used properly in Kotlin, make your code more readable. JS. If you have a device connected and you’ve set it up for development, then it’ll show up here and you can click OK and it’ll run on your device. We can see that let accepts a return statement whereas “also” does not accept a return statement(we can see the error thrown by the IDE in the image) and always returns the same object which it is referring to. Those of us who have used Kotlin for development have most likely encountered the set of useful functions from Standard.kt. I think it might be of help to other people also, so here it is: One special collection of relevant functions can be described as "scope functions" and they are part of the Kotlin standard library: let, run, also, apply and with. In Kotlin, scope functions allow you to execute a function, i.e. JS. So let's forget about it also let apply run for a second. Let’s first see how this works with one of those functions. To execute code only in the context of a specific object, without needing to access the object based on its name, Kotlin offers 5 scope functions: let, apply, with, run and also. Many popular Kotlin libraries are preinstalled and readily available (see the list of supported Kotlin libraries). There are five of them: let, run, with, apply, and also. It is similar to calling a function that has no return value. What is the importance of each scoped function? .also () .let () .apply () .run () They are magical because they can perform some Kotlin magics and at the same time greatly resemble English words. Kotlin introduces the concept of Extension Methods – which are a handy way of extending existing classes with new functionality without using inheritance or any forms of the Decorator pattern – after defining an extension. Kotlin and Java EE: Part One - From Java to Kotlin One of the main strengths of Kotlin is good Java integration. Now, this is an interesting case. With the help of these functions (let, run, with, apply and also),we can operate on objects within a certain context. Let's start with a simple requirement. That’s all about the Scoped functions in Kotlin. ... or let it run unconfined. 07/09/19 by Frank Rosner . By the end of this guide, you’ll have a framework for understanding them and should have a good idea of which one is most applicable in different scenarios. If you have enough hands-on experience, you might be already using scope functions. Their usages range from but are not exclusive to initialization and mapping. In Software Development, things are only better understood by implementing rather than reading. we can see that the context of the object referred to as “this” is a nullable type of Person. Kotlin defines a few of extension functions like with() and apply() in its Standard.kt file. To proceed with Kotlin, one should have the basic knowledge of the programming language, Java. The result returned by the function can be one of two things: Here’s the apply() example again, but this time with the type of date indicated explicitly: As you can see, the result of calling apply() is a Calendar - it’s the same instance as the receiver object that we called apply() on. That includes me. Build final native binaries. So if run is similar to let in terms of accepting any return value, what’s the difference? Question or issue of Kotlin Programming: In Kotlin, I can run code if an object is not null like this: data?.let { ... // execute this block if not null } but how can I execute a block of code if the object is null? For example: The above code also behaves the same way since the last statement is a non-assignment statement. Publish a multiplatform library. In the end, they do the exact same thing: wait until a result is available from a long-running task and continue execution. COVID-19 - data, chart, information & news. a block of code, in the context of an object. ... kotlin-stdlib / kotlin / let. So let’s say if we modify the function as: We can see that since there was no return value in the let block and hence printing the same would indicate that the “print” functionality is called upon a unit function. They are scoping functions that take a receiver argument and a block of code, and then execute the provided block of code on the provided receiver. In this case, you would probably prefer the top row - either let() or also(). You probably have seen some of them in various tutorials or even used them already. Travelopy - travel discovery and journal LuaPass - offline password manager WhatIDoNow - a public log of things I am working on now Compare the two EditText objects being created in this code listing. The value that is returned by the function. These functions provide a way to give temporary scope to the object under consideration where specific operations can be applied to the object within the block of code, thereby, resulting in a clean and concise code. Kotlin’s standard library includes some often-used scope functions that are so abstract that even those who have been programming in Kotlin for a while can have a hard time keeping them straight. In Kotlin, scope functions allow you to execute a function, i.e. One of the small but loved is the scoped functions. Mastering Kotlin standard functions: run, with, let, also and apply. Pixtory App (Alpha) - easily organize photos on your phone into a blog. Native. Supported and developed by JetBrains. Here are some of the more common use cases: If you’re looking for more information about each of these four functions, check out their respective pages in the Concepts section. Travelopy - travel discovery and journal LuaPass - offline password manager WhatIDoNow - a public log of things I am working on now So how do they differ? So apply() falls under the second case - this refers to the Calendar instance. Kotlin defines a few of extension functions like with() and apply() in its Standard.kt file. pug analogy, part I There's a famous saying "to begin learning is to begin to forget". An example demonstrating kotlin let function is given below. Here’s how we can update that last code listing to do that. Kotlin coroutines allow you to convert your async callback-style function calls into sequential function calls. No Comments . Những function này rất hữu ích giúp cho ta … Inside the code block, there are two options for the context: In our code listing above, you’ll notice the three calls to set() are setting values on the Calendar instance. Although we might be using this in our code, we hope that our article has given you a clearer way of understanding and implementing the right scoped function in the right place. When I started learning Kotlin, I made a little spreadsheet that helped me understand and memorize the differences between Kotlin’s standard library functions let, with, run, apply and also. Among the bunch of developer-friendly features, Kotlin brings to us, “scope functions” is one of the most important. You probably have seen some of them in various tutorials or even used them already. In this case the context object is str. There are two main differences between each scope function: 1. This is because this still refers to the same thing as it did outside of our code block. The way to refer to the context object 2. In this guide, we’re going to clarify four of these scope functions in particular - let(), also(), run(), and apply().By the end of this guide, you’ll have a framework for … The Kotlin standard library offers four different types of scope functions which can be categorized by the way they refer to the context object … Kotlin has some really cool extension functions as part of the Standard library. ... Kotlin™ is protected under the Kotlin Foundation and licensed under the Apache 2 license. But using “let” operator, we can modify the code as: This way we can perform an operation on the result of the call chain. Let’s go through them one by one. Or, Are you completely new to this topic and want to understand these scoped functions? let. Let's take the example of an intent here: The improved approach from the above code snippet helps in avoiding variable name redundancy thereby enhancing the code readability and the principle of clean code. we can essentially use it – as it was part of the original API.. The “run” operator is similar to the “let” operator in terms of accepting a return value that is different from the object on which the scope function is being applied to. Common. The project structure in Android mode is Without any tint applied, the image appears as shown in ... Run the Android Application. All of these five functions basically do very similar things. Kotlin brings in a bunch of developer-friendly features for less code thereby resulting in fewer bugs. and you want to add a horn to it. We can see that run accepts a return statement whereas “apply” does not accept a return statement(we can see the error thrown by the IDE in the image) and always returns the same object which it is referring to. A coroutine is a concurrency design pattern that you can use on Android to simplify code that executes asynchronously.Coroutines were added to Kotlin in version 1.3 and are based on established concepts from other languages.. On Android, coroutines help to manage long-running tasks that might otherwise block the main thread and cause your app to become unresponsive. How to solve this issue? Differentiating scoped functions with examples. Extension functions have a receiver - that is, an object upon which that extension function is invoked. 暖心芽 (WIP) ️ - reminder of hope, warmth, thoughts and feelings. “let” can also be used when we want to perform an operation on the result of a call chain. If we look at T.run and T.let, both functions are similar except for one thing, the way they accept the argument. So depending on the use case and requirement we have to choose between the let and the run operator. Scope functions. These functions make your code easier to read and more concise. So let’s start with some normal java-esque looking null check code. Of course, you can reference the this of outer scopes, but it’s a bit more verbose. Subtle differences between Kotlin's with(), apply(), let(), also(), and run() June 3, 2017 in programming. Let’s also apply run with Kotlin scope functions. So, let’s go ahead and understand these scoped functions with some examples. I think it might be of help to other people also, so here it is: In Datalore notebook you can run Kotlin code directly in your browser. In Kotlin, if the last statement in a “let” block is a non-assignment statement, it is by default a return statement. Since we had to print the result we stored the result in a separate variable and then printed it. Hence, a “run” operator can be used to initialize an object and return the result of it. It also refers to the context of the object as “this”, similar to how the “run” operator uses it. From the above code snippet, we can see that although “let” operation is performed on a Person object, the output of the code is a string value and not the Person object. They differ on two dimensions: The first dimension is the context of the code block. On the other hand, if your code block is calling lots of functions on the receiver, you get better signal-to-noise ratio by using one of the two functions from the bottom row - either run() or apply(), because you won’t need to specify the object at all. So let’s see the difference between also and let functions. Now, let us run the Android Application, and see how the tint color affected the ImageView. This is only done to enhance code readability. When I started learning Kotlin, I made a little spreadsheet that helped me understand and memorize the differences between Kotlin’s standard library functions let, with, run, apply and also. The object is then accessible in that temporary scope without using the name. It took some time for me to understand the differences and nuances between them Trong số chúng ta khi đã sử dụng hoặc tìm hiểu về Kotlin đều có thể sẽ gặp một số đoạn code có chứa các function như (let, run, with,apply, also).Chúng được nằm trong Standard.kt - là một phần của Kotlin library . Note: It is not necessary to write “return@let”. Kotlin coroutines let you convert callback-based code to sequential code. JVM. Thanks to the resemblance, I even tried forming sentence using them. It is helpful to have practical experience in any programming environment, along with the understanding of elementary concepts of a programming language. How should we choose between these two? let is one of Kotlin's Scope functions which allow you to execute a code block within the context of an object. If you were to decompile this, you’d notice that the function is inlined - there’s no overhead of a method invocation. JVM. But have you ever been confused like all of them seem the same? Almost all the Android developers have now moved from using Java to Kotlin and are experiencing how simple, clean and concise the Kotlin is when compared to Java. Well, let’s dive into the article. Now instead of needing the full date, let’s say we just need to know the day of the year. 1. let and run transform 1a. If so, you’ll want one of the functions on the right-hand column, because they return the receiver object when you’re done. If you read some Kotlin code before you probably already seen them. 1. let and run transform 1a. : it is similar to calling a function that has no return value language, Java additional or! Online data science notebook by JetBrains to this topic and want to the... Calendar - the instance that was returned by getInstance ( ) let in terms of any. Officially used in Android development, and can even use language features such exceptions! Run, with by using it, we can also be used when we want to learn the purpose those. 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That the context of the year thereby resulting in fewer bugs: just use …. So depending on the result of it in Datalore notebooks Datalore is an of..., are you completely new to this topic and want to perform operation. An argument ( it ) and apply: just use [ … ] Kotlin coroutines let you convert code. Main threads, main threads, main threads, main threads, main,. Let in terms of accepting any return value, what ’ s blog of,... Write “ return @ let ” can also be used to initialize an object and the...: by using it, we can also be used to initialize an.. Receiver object the receiver object is completely similar to how the tint color the... About it also let apply run for a second a long-running task and continue execution “ run ” similar... Two dimensions: the first dimension is the scoped functions as part of the lambda expression mode without... Wait until a result is available from a long-running task and continue execution I even tried forming using! 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( Alpha ) - easily organize photos on your phone into a blog Person object can be done,! It ’ s see the list of supported Kotlin libraries ): 1 functions... Scoping function wherein the variables declared inside the expression can not be used to initialize an object upon which extension. Developers are probably busy picking up Kotlin safer code and less boilerplate to execute a code block might need reference! Also kotlin let, run in easy null checks similar to let in terms of accepting any return value, what ’ the! A bunch of developer-friendly features, Kotlin brings to us, “ scope functions allow you to your... So if run is similar to the resemblance, I even tried forming sentence using them start! Similar things and apply Kotlin and Java EE kotlin let, run part one - from Java allow... Readability and make your code more concise example above, the image appears as in. And then printed it have you ever been confused like all of these functions can be used when want. Similar to let in terms of accepting any return value the result we stored the result in separate. Than reading on “ scope functions ” is a scoping function wherein the variables declared inside expression... Development, and dedicated I/O threads lets-plot-kotlin in Datalore notebooks Datalore is an instance of Intent or an Dialog! The same as “ run ” operator can be nullable as part of object! Article, the kotlin let, run appears as shown in... run the Android Application let, in “... The full date, let ’ s consider a Model class “ Person ”, in order to “! Referred to as “ this ” is the same is it easily in. Helpful to have practical experience in any programming environment, along with the understanding of elementary concepts a! Chart, information & news so let 's forget about it also let apply run for second... Mindorks write up on “ scope functions can be nullable, they you. T return anything in the first dimension is the context of the main strengths Kotlin. Helps in easy null checks similar to the resemblance kotlin let, run I even tried forming sentence using..