Ext JS 4: Custom object property value based on condition - object

Question

I'm trying to create custom property values (based on a condition of a function) for my Ext objects, instead of specifying just a value.
Example 1:
old code (working)
this.buttons = [
{
text: 'Save',
new code (not working)
this.buttons = [
{
text: function() {
return 'Save X';
},
Example 2:
old code (working)
}, {
width: 270,
labelAlign: 'right',
xtype: 'textfield',
name: 'user_id',
fieldLabel: 'User ID',
hidden: true
}]
new code (not working)
}, {
width: 270,
labelAlign: 'right',
xtype: 'textfield',
name: 'user_id',
fieldLabel: 'User ID',
hidden: function() { return true; }
}]
Example 3:
Ignore entire textfield object (lazy instance) completely based on a condition:
}, {
width: 270,
labelAlign: 'right',
xtype: 'textfield',
name: 'employee_number',
fieldLabel: 'Employee Number'
}]

Answer 1

You simply can't do it this way. It is not possible to replace a type with a function. In your case you assign a function reference to a variable which is expected to be boolean, same for the string.
Solution A.
You should consider to write yourself a field factory. Within that factory you can then execute any function before assigning configs. (Sort of same then B but can be used to reduce function calls)
Solution B.
Use a function reference itself. This one should then get executed. (spare the requirement of class extension and is over that reuseable)
// The data store containing the list of states
var states = Ext.create('Ext.data.Store', {
fields: ['abbr', 'name'],
data : [
{"abbr":"AL", "name":"Alabama"},
{"abbr":"AK", "name":"Alaska"},
{"abbr":"AZ", "name":"Arizona"}
//...
]
});
Ext.namespace('my.util.helper');
my.util.helper.decideHide = function() { return true; }
// Create the combo box, attached to the states data store
Ext.create('Ext.container.Container', {
renderTo: Ext.getBody(),
items: [{
xtype: 'combo',
fieldLabel: 'Choose State',
store: states,
queryMode: 'local',
displayField: 'name',
valueField: 'abbr',
test: my.util.helper.decideHide(),
listeners: {
afterrender: function(n) {
alert(n.test);
}
}
}]
});
Solution C.
And the solution I use most in such cases are simplified if else statements
// ... // more code
{
    text: myCondition ? 'Text A' : 'Text B',
// more code
}
// ... // more code

Answer 2

Yeah that is not going to work, some Ext configs take a function that will be evaluated but most of them don't. Instead of creating anonymous functions and not invoking them I would do something like this:
Ext.define('UserPanel', {
extend : 'Ext.panel.Panel',
initComponent : function() {
this.items = [{
xtype : 'button',
text : this._getSaveButtonText()
}, {
width : 270,
labelAlign : 'right',
xtype : 'textfield',
name : 'user_id',
fieldLabel : 'User ID',
hidden : this._isUserIdHidden()
}]
this.callParent();
},
_getSaveButtonText : function() {
return 'Save';
},
_isUserIdHidden : function() {
return true;
}
});