Looks like we can't reproduce the issue or there's a problem in the test case provided.
  1. #1
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    Default States of object is not maintained when multiple instances of a class are created

    States of object is not maintained when multiple instances of a class are created


    REQUIRED INFORMATION


    Ext version tested:
    • Ext 4.1.1

    Browser versions tested against:
    • Any

    DOCTYPE tested against:
    • n/a

    Description:
    • I ran into an issue that took quite some time to debug in our application. I have isolated it to the fact that when one creates 2 instances of a class the state of the first instance is lost and replaced by the state of the second one. This is happening when the class is defined by passing a function instead of an object as the second parameter to Ext.define as documented in extjs-4.1.1/docs/index.html#!/api/Ext-method-define

      I have reproduced it with the simple class below

    Steps to reproduce the problem:
    • try code below
    • you will see that when the second instance is created the name property in the first instance takes the value of the one in the second instance

    The result that was expected:
    • each instance to have its own state

    Test Case:

    Code:
    Ext.define('test.class.PrivateExample',function(){
     var itsName = 'defaultName';  // this is private
    
    function constructor(a) { if ( a !== undefined && a.name !== undefined ) {itsName = a.name;}}
    
    function privateFct1() {return itsName;}
    
    // The public API to this class
    return  { publicFunction1: privateFct1, constructor: constructor	}
    });
    
    
    function testPrivateExample() {
    var testObject = Ext.create('test.class.PrivateExample',{name: 'test1'});
    console.log ( "First Object: name: " + testObject.publicFunction1() );
    var testObject2 = Ext.create('test.class.PrivateExample',{name: 'test2'});
    console.log ( "Second Instance: name: " + testObject2.publicFunction1() );
    console.log ("  Now you see that first instance name is incorrect ! ");
    console.log ( "First Instance: name: " + testObject.publicFunction1() );
    }


    HELPFUL INFORMATION


    Screenshot or Video:
    • attached

    See this URL for live test case: http://


    Debugging already done:
    • none

    Possible fix:
    • not provided

    Additional CSS used:
    • only default ext-all.css
    • custom css (include details)

    Operating System:
    • ________
    • any

  2. #2
    Sencha - Senior Forum Manager mitchellsimoens's Avatar
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      0  

    Default


    The function is executed when the class is defined. If you didn't create any instances you will be able to see the function is executed, so the itsName variable is then shared.
    Mitchell Simoens @SenchaMitch
    Sencha Inc, Senior Forum Manager
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  3. #3
    Sencha - Ext JS Dev Team evant's Avatar
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      0  

    Default


    This isn't a bug, you've just created a closure.

    It's similar to doing this:

    Code:
    (function(){
        var name = 'foo';
        
        Ext.define('MyClass', {
            
            constructor: function(cfgName) {
                name = cfgName;
            },
            
            fn: function(){
                return name;
            }    
        });
    })();
    
    Ext.onReady(function() {
        var o1 = new MyClass('foo'),
            o2 = new MyClass('bar');
            
        console.log(o1.fn(), o2.fn());
    });
    Evan Trimboli
    Sencha Developer
    Twitter - @evantrimboli
    Don't be afraid of the source code!

  4. #4
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      0  

    Question hold on...

    hold on...


    Mitchell,

    If it is not a bug, here are some additional questions/comments:

    1) I would think the doc needs to be made clearer (http://docs.sencha.com/ext-js/4-1/#!...-method-define). In particular, the example provided gives the impression that passing a function is equivalent to passing an object literal but simply provides a mechanism to make properties/functions private.

    2) Then, what is the official/supported technique to have private properties/functions?

    thanks.

  5. #5
    Sencha - Ext JS Dev Team evant's Avatar
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      0  

    Default


    1) This is a fairly common JS pattern, it's not suggesting that they are "private" as in instance variables, but "private" as in local to that function scope (it's a closure).

    2) If you absolutely ~must~ have private members, you could do something like this (not recommended):

    Code:
    Ext.define('MyClass', {
        constructor: function(cfgName){
            var private = 0,
                name = cfgName;
            
            this.getPrivate = function(){
                return ++private;    
            };
            
            this.getName = function(){
                return name;
            };
        }
    });
    
    Ext.onReady(function(){
        var o1 = new MyClass('Foo'),
            o2 = new MyClass('Bar');
            
        console.log(o1.getPrivate(), o1.getName(), o1.private, o1.name);
        console.log(o2.getPrivate(), o2.getName(), o2.private, o2.name);
    });
    Evan Trimboli
    Sencha Developer
    Twitter - @evantrimboli
    Don't be afraid of the source code!

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