Kotlin scope function Let, Run, With, apply and also

What is the use ?

The main purpose is to execute a block of code within the context of an object. There are 5 scope function. I’ll keep this short and simple lets start without wasting more time

1. Let

Used to check null, also better than simple null check in multi-threading and returns last line of this scope

var number: Int? = null     //initialize with some value for result
var result = number?.let {  //lambda func with it:Int as param
    var square = it * it    //'it' is copy of number
    square                  //let will return last line
}

2. Also

Same as ‘Let’ but it doesn’t return the last line as ‘Let’, instead it returns the object it was called on.

var number: Int = 2         //init
number = (++number).also {  //takes expression also
    ++it                    //return the object it called on"number"
}

3. Apply

Helpful function to modify objects, it uses ‘this’ instead of ‘it’ as we work inside Class of object

var intent = Intent().apply{this:Intent  //this means object intent
    putExtra("", "")                     //putExtra of intent object
    putExtra("","")
    action = ""                          //return same object 'this'
}

4. Run

Equivalent to apply, but it won’t return the object it was called on, instead it will return the last line

var intent = Intent().run{
    putExtra("", "")
    putExtra("","")
    action = ""             //return last line
}

5. With

Same as ‘Run’ but with different signature

with(Intent()){            //with(arg) here with needs argument
    putExtra("", "")
    putExtra("","")
    action = ""
}

All these scoped function do very similar things, but this make code more concise and readable.

Hiding Secret/Api key in Android

AsyncTask is deprecated in Android 11/R

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