Ext 表单控件为空时自动加星号 *

Ext.form.Field.prototype.initComponent = function(){       
        if(this.allowBlank==false){
            this.fieldLabel="*"+this.fieldLabel;
        }
        Ext.form.Field.superclass.initComponent.call(this);
        this.addEvents(
           
            'focus',
           
            'blur',
           
            'specialkey',
           
            'change',
           
            'invalid',
           
            'valid'
        );
}