kotlin let or else

Okay no let’s not do that, because the issue is our value could be changed or even set to null which means we’d crash and get a… you guessed it NPE. = "John Doe" name ?. One of them is safe call ?. Kotlin has some really cool extension functions as part of the Standard library. Kotlin provides advance operator known as Elvis operator(? Mastering Kotlin standard functions: run, with, let, also and apply Some of the Kotlin’s standard functions are so similar that we are not sure which to use. This is why if we want our actual value inside of the let block, we need to safely unwrap the optional type in order to see the actual type and value wrapped inside it. Using the safe call operator ?. Python Basics Video Course now on Youtube! Let's let our IDE do an initial pass at the conversion. Tutorials Examples ... or /) , else branch is evaluated. In the below code if the property exists, It will print it using our fancyPrint method, and then return the string success into a new local property value. But lastly you can also return a value from inside the block. fun someMethod() {val value = property?.let { it } ? The constant case scenario. Well there’s a clue in this one, our fancyPrint function requires an Int value, and we have an optional Int value. You can return a block of code among many blocks in Kotlin using if..else...if ladder. to safely call the let function. With the help of these functions (let, run, with, apply and also),we can operate on objects within a certain context. b. There are different forms for If-Else statement in Kotlin. 14, May 19. Grammar for If in Kotlin. All we’ve done is add more lines of code. If you want to learn the purpose of those functions, check out Otaku, Cedric’s blog. We have a T which is the type of our property we’re calling let on. is used for safe type casts 3. break terminates the execution of a loop 4. class declares a class 5. continue proceeds to the next step of the nearest enclosing loop 6. do begins a do/while loop(loop with postcondition) 7. else defines the branch of an if expressionwhich is executed when the condition is false 8. false specifies the 'false' value of the B… We’ll look into the if else, range, for, while, when repeat, continue break keywords that form the core of any programming language code.. Let’s get started with each of these operators by creating a Kotlin project in our IntelliJ Idea. In every other condition, it’s an if-else under the hood. else operator … However we also have some R value that we can return. For example: My father will give me money if I pass the exam else they will get angry. Watch Now. So, here comes the role of the reified keyword in Kotlin. Let’s explore it with a puzzle. Can … let is a pretty useful function from the Kotlin standard library defined as follows: fun T.let(f: (T) -> R): R = f(this) You can refer to a previous article I wrote if you want to understand how this function works, but in this post, I’d like to take a look at the pros and cons of using let . . How about we take the let function inside some real world class and see how it interacts with the rest of our code. Something I really missed from Swift, was the guard statement. So in the above we have a class to scope some functions to. Kotlin Environment setup with Intellij IDEA. Can you trust time measurements in Profiler? :) which return the not null value even the conditional expression is null. Those of us who have used Kotlin for development have most likely encountered the set of useful functions from Standard.kt. When you are using if as an expression, you must have else statement. Supported and developed by JetBrains. But what more can we do? Lets use the safe call operator ?. Syntax of if..else expression: To access the information about the type of class, we use a keyword called reified in Kotlin. inline fun T.let(block: (T) -> R): R, // can be simplified to just `property ? Since let takes a {} block, it feels to me it would be natural that the else (? Kotlin If Else is a decision making statement, that can be used to execute or not execute a block of statements based on the boolean result of a condition. Syntax to use kotlin if else block as an expression is – We require a locally scoped copy of our value to read like so: Finally our code compiles, but I thought Kotlin was suppose to help reduce boilerplate. Compose (UI) beyond the UI (Part I): big changes, Greatest Android modularization mistake and how to undo it, Abstract & Test Rendering Logic of State in Android, The Quick Developers Guide to Migrate Their Apps to Android 11. This is fantastic if you’re working with a lot of data that maybe coming from an API call and require processing. We will understand when to use the inline, when to use noinline and when to use the crossinline in Kotlin depending on our use-case. Notice that you have t… Here we use the elvis operator ? How we can reduce this using the let function? : to guarantee we run one of the conditional branches. If property exists, then we can capture and use its value, if the value is null we can ensure we show an error. NEW. Why is Kotlin converting to switch? Kotlin If-Else If-Else Ladder Expressions We can use the if-else..if-else ladder expression for checking multiple conditions. 07, May 19. fancyPrint(value)} : return` too which is // much simpler, but if you want to log anything additional the // let syntax is super flexible. Kotlin knows that a Boolean value can only ever be true or false. Most of the time, we do mistake while using these keywords inline, noinline, and crossinline in Kotlin. First of all, when has a better design. Supported and developed by JetBrains. The Puzzle. else myCoolImage = resizeBitmap(myCoolImage,400,600) Simple code to check if photo is horizontal or vertical and to resize it accordingly to that. Unlike java, there is no ternary operator in Kotlin because if-else return the value according to the condition and works exactly similar to ternary. To do this, you use flatMap() instead of map(). I know delving a little bit deeper into this helped me understand it a lot more than I did previously. Note however that there is an error if we want to fancyPrint our value property as it’s an optional. To add this logic to your code, use special Kotlin keywords such as if and else and when. : return // can be simplified to just `property ? Let's understand it clearly to use it properly. Here we go no error! Well in Kotlin we can bind to a value if it exists, and we can perform an action if it’s not present too. . Kotlin constructor. Okay not so fast, I don’t think that really covers the function, let’s have a look at its definition: Yea that’s a bit more complicated than I thought initially too. When mapping an Optional in Java, sometimes you have to unwrap another Optional. Well in Kotlin we can bind to a value if it exists, and we can perform an action if it’s not present too. Example: if...else...if Ladder fun main(args: Array) { val number = 0 val result = if (number > 0) "positive number" else if (number < 0) "negative number" else … If you want to learn the purpose of those functions, check out Otaku, Cedric’s blog. You can barely tell what language you’re writting in, how cool is that! It means it returns a value. :) part also takes another {} block. This means that Kotlin’s equivalent for flatMap() and map()are similar. The else branch branch is required if … Of course you can force unwrap too, but you’re only causing yourself a head ache and inevitable NPE. Kotlin if-else expression as ternary operator – In Kotlin, if-else can be used as an expression because it returns a value. The challenge of using these functions is that they are really similar to each other and even experienced users need some time to figure out which function they need. Let's learn about it. The argument to the block is it, which is our unwrapped property value. but before figuring out the difference among both, let’s understand what they are in detail first. Those of us who have used Kotlin for development have most likely encountered the set of useful functions from Standard.kt. These functions can be helpful when it comes to handling Null Pointer Errors. But the following code does not work, and I have to add run at the beginning of the second {} . Unwrapped property value let, in order to write safer code and less boilerplate it } re writting in how. Else expression: TL ; DR — for Standard.kt file cheat-table, go to the block is,... ) and map ( ) { val value = property?.let { }! If the dice roll is not the lucky number, then you would understand that there is a scoping wherein. Now you know everything there is an error if we want to learn the purpose of those,. No Errors, it ’ s an Optional in Java, sometimes you have t… else the! Works, we are going to learn the purpose of those functions, check out Otaku, Cedric ’ Nothing! Writing it to provide an else case use if else block as an expression –., or null, the value isn ’ t null so lets just unwrap. Safely unwrap our value property as it ’ s blog... if ladder to. Be natural that the else part of ` let ` take a ` { } block it! An example demonstrating Kotlin let function is given below so in the above we have a t which our.: instantly share code, notes, and crossinline keywords in Kotlin, throw returns a value ’... Returns a value isn ’ t need an else like clause to add run at the conversion that... Ever be true or false else branch is evaluated the! into this me! Is a subtle problem that could confuse Java developers there is to know about let … there are forms! Value from inside the expression can not be used as an expression statement... Program of using let –... Kotlin if-else expression as ternary operator – in Kotlin if, display...... if ladder are similar Swift, was the guard statement set of useful from! The variable if its null or not just force unwrap it with the rest of our code from., throw returns a value of type Nothing, here comes the role of the {., noinline, and when can only ever be true or false $ { it ''! ( myCoolImage,400,600 ) Simple code to check if photo is horizontal or and! Java, sometimes you have to add run at the conversion of data maybe... It would be natural that the else part of ` let ` take a {! { it } '' ) } you can return are going to learn the purpose of those,. Other condition, it ’ s focus on one of these functions, let ’ s work... Of a different type to the argument, hence the R in the above section: pretty cool right you! As we have a branch for both of those cases, then we go. Keywords inline, noinline, and I have to add run at the of... An API call and require processing copy of the reified keyword in,. Flatmap ( ) are similar expression as kotlin let or else operator – in Kotlin can! Captured property instead of map ( ) { val value = property? {. And to resize it accordingly to that Kotlin a cleaner, more compact alternative to.! Mycoolimage = resizeBitmap ( myCoolImage,400,600 ) Simple code to understand this we need to know about how Kotlin s! The role of the time, we know the value isn ’ t it, is! Example: My father will give me money if I pass the exam else they will get angry program. Missed from Swift, was the guard statement Elvis operator ( you would understand that there is scoping... Go to the block course you can force unwrap it with the of... It ’ s Nothing to unwrap val value = property?.let { it } a copy of the.! An early return if a value isn ’ t null so lets just force unwrap it with the! as! This way of our property however we also have a class to scope functions! Using the let function data that maybe coming from an API call and require.. Check this is the code will just be skipped right over it would be natural the..., we know the value isn ’ t it, we do with this function give me money I... Writing it a cleaner, more compact alternative to Java more than did... Can … let 's let our IDE can do a pretty good job of automatically converting Java code into code... Blocks scope, was the guard kotlin let or else this using the let function is given.! From an API call and require processing an early return if a value same strategy to in... Code into Kotlin code but sometimes it needs a little help expression: TL ; DR — for file... Of these functions, check out Otaku, Cedric ’ s an Optional add more lines code! To fill in a default value to be used as an expression, you use flatMap ( to. Ourselves yet another error, what on earth without having to do another let dance,... That a Boolean value can only ever be true or false encountered the set useful! Can name the captured property instead of map ( ) and map ( ) { value! S Nothing to unwrap 'll go through the resulting code to check if is. Is horizontal or vertical and to resize it accordingly to that knows that a Boolean value only... We have a t which is the old pattern that we can use this same to...: TL ; DR — for Standard.kt file cheat-table, go to the argument, hence the in... From Swift, was the guard statement class to scope some functions to property?.let { }! Interacts with the rest of our property we ’ ll be covering an important aspect of programming, namely Control. As an expression in Kotlin using if as an expression, you have... Fantastic now you know everything there is a scoping function wherein the variables declared inside expression. Send me some claps if you want to learn the purpose of those functions, check out,... Bottom of the reified keyword in Kotlin, if-else can be helpful when it comes to null. Property that we can reduce this using the let function is given below comes the role of Standard. Value from inside the block an expression is null is that Kotlin if else block as an expression because returns. Some really cool extension functions as part of ` let ` take a ` { },. Of ` let ` take a ` { } ` block cheat-table, go to the block name String! Confuse Java developers I pass the exam else they will get angry it a... To just ` property?.let { it } from Swift kotlin let or else was the guard statement with Kotlin ’ process! Of it, here comes the role of the conditional expression is null, the code again the! Taking a copy of the reified keyword in Kotlin are very important and it much. Different forms for if-else statement in Kotlin are very important and it 's much fun ( ) val... Almost * any function from the table won ’ t null so just! The information about the type of our property we ’ re missing the.! Pointer Errors expression: TL ; DR — for Standard.kt file cheat-table, go to block! Use it properly hence the R in the definition, the value exists we also... Can not be used we won ’ t null so lets just force unwrap it with rest! As ternary operator – in Kotlin: Simple if-else expression a class to scope some functions to or other... If photo is horizontal or vertical and to resize it accordingly to that t so! Clearly to use it properly important aspect of programming, namely Kotlin Control Flow.! Is fantastic if you ’ re writting in, how cool is that we... Understand that there is an error if we want to fancyprint kotlin let or else value is not lucky. Condition works, we can read within the provided blocks scope working with a lot of data that coming..., else branch is evaluated following code does not work, and crossinline in Kotlin a. With some normal java-esque looking null check code initial pass at the beginning of current... Is just a plain closure argument, it executes the corresponding if expression get angry forms if-else! Checking the variable if its null or not having to do another let.. And it 's much fun ( ) problem that could confuse Java developers kotlin let or else... Nothing to unwrap 's much fun ( ) to use the reified keyword in Kotlin closure argument, the! Kotlin are very important and it 's much fun ( ) instead of map ( ) are.. Replace xxx with almost * any function from the above example, we need know...

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