Use static variable in function()

Question

I would know if we can declare a static var in a function, as we can do in JavaScript.

When I callback my function, my variable keep her last affectation.

Or

Answer 1

You can't use static in a function.

Global variables in Dart are no code smell because they are only library global.
Global variables in JavaScript are ugly because they can conflict with global variables from 3rd-party libraries.
This doesn't happen in Dart.

As you can make a library in Dart as small as you want (for example only one variable) and you have something similar to a namespace for a library when you import it like

import 'my_globals.dart' as gl;

and then use it like

print(gl.myGlobalValue);

this is no code smell.

You could also create a class to simulate a namespace like

class MyGlobals {
  static myVal = 12345;
}

But library global variables are preferred in Dart instead of classes which contain only static variables or functions.

Answer 2

You can use only global variables.

Also you may solve this via private variables with "mangling" names.

void main() {
  myFunction();
  myFunction();
  myFunction();
}

int _myFunction$count = 0;

void myFunction() {
  print(_myFunction$count++);
}

This does not helps a lot but you can consider that variable with name "_myFunction$count" is a local static variable "count" in function "myFunction".

The same as this pseudo code.

void myFunction() {
  static int count = 0;
  print(count++);
}

Answer 3

You can use Closures, in this example I have created a counter as follows:

void mian(){
 var my_counter = counter(5);
 for (var i = 0; i < 10; i++) {
   print(my_counter());
 }
}

Function counter(int n) {
  var number = 0;
  var func = () {
    if (number < n) {
      number++;
      return number;
    } else {
      number = 1;
      return number;
    }
  };
  return func;
}

or also a Generator:

Iterable<int> count(int n) sync* {
  var number = 0;
  while (number < n) {
    yield number++;
  }
}

Answer 4

You can use a function object to maintain state:

library test;

class Test implements Function {
  var status = 0;
  static var static_status = 10;

  call() {
    print('Status: $status');
    print('Static status: $static_status');
    status++;
    static_status++;
  }
}

void main() {
  var fun = new Test();

  fun();
  fun();
  fun();

  var fun2 = new Test();

  fun2();
  fun2();
  fun2();
}

Output:

Status: 0
Static status: 10
Status: 1
Static status: 11
Status: 2
Static status: 12
Status: 0
Static status: 13
Status: 1
Static status: 14
Status: 2
Static status: 15