How can I implement a method that change directly the value this with dart extension?-CodePudding

I want to know how can I change/affect the value of this with dart extensions without returning a value.

For example, when I do this :

"example text".cutFirstLetter();

by just executing it, I want its String value for the rest of the code to be "e", I don't want it to be returned in function, I want the whole of it to change.

let me more explain :

extension ExmapleExtension on String {
    String cutFirstLetter() {
        return this.substring(0, 1);
    }
}

this will work only as returned value, so it will work on places that expect the return such as print("example text".cutFirstLetter()); or if I assigned to another String such as String newExampleText = "example text".cutFirstLetter();

I want when I just call it in a line, it will execute it on the this referred String

I tried something like:

extension ExmapleExtension on String {
    removeTletter() {
        this = this.substring(0, 1);
    }
}

but it throws an error.

CodePudding user response：

First, strings are immutable. Perhaps you've noticed there are no methods in the String class that change the value of the string "in-place". They all return values (often other Strings).

Second, you cannot assign to this, only call methods on it.

So you'll have to be happy with just returning a new value.