ext继承的两种写法

转自：http://liuna718-163-com.iteye.com/blog/805377
在使用extjs时，因为特殊的业务要求，extjs提供的功能不能满足业务逻辑，所以需要对其进行扩展，也就是所谓的继承，
在extjs中继承有两种写法
1。在ExtJS中使用Ext.extend()函数实现继承功能：

/* 
*扩展树的多选模式，加了写业务逻辑方法validNodeHasFolder，并重写了select方法加入了业务逻辑 
**/  
Ext.ns("Ext.targsoft");  
Ext.targsoft.MultiSelectionModel = function(config){  
    Ext.apply(this, config);  
    Ext.targsoft.MultiSelectionModel.superclass.constructor.call(this);  
};  
  
  
Ext.extend(Ext.targsoft.MultiSelectionModel , Ext.tree.MultiSelectionModel,{  
    validCount : 0 ,  
      
    select : function(node, e, keepExisting){  
        if(keepExisting !== true){  
            this.clearSelections(true);  
        }  
        if(this.isSelected(node)){  
            this.lastSelNode = node;  
            return node;  
        }  
        if(!node.isLeaf() && keepExisting ){  
            return ;      
        }  
          
        if(keepExisting && node.isLeaf() && this.validCount == 0 ){  
            alert(this.validCount );  
            this.validNodeHasFolder();  
        }  
          
         
        this.selNodes.push(node);  
        this.selMap[node.id] = node;  
        this.lastSelNode = node;  
        node.ui.onSelectedChange(true);  
        this.fireEvent("selectionchange", this, this.selNodes);  
        return node;  
          
          
    },  
    //判断选择的节点中是否含有文件夹，如果有那么就进行反选  
    validNodeHasFolder : function(){  
        this.validCount = 1 ;  
        for(var i=0 ; i< this.selNodes.length ; i++){  
            if(!this.selNodes[i].isLeaf()){  
                this.unselect(this.selNodes[i]);  
            }  
        }  
    }  
  
});  

2.Extjs中替换constructor，写法如下：

Ext.ns('Ext.formdesign');  
Ext.formdesign.FormSort = Ext.extend(Ext.Window ,{  
        constructor : function(_cfg){  
            Ext.apply(this,_cfg);  
            this.grid = this.createGrid();  
            Ext.formdesign.FormSort.superclass.constructor.call(this,{  
                title : '表单类别' ,  
                width : 280 ,  
                height : 270 ,  
                closeAction : 'close' ,  
                items :  [this.grid ] ,  
                buttons : [  
                    {  
                        text : '关闭' ,  
                        scope : this ,  
                        handler : function(){  
                            this.close();  
                        }  
                    }  
                ]  
            })  
    },  
      
    //创建表格  
    createGrid : function(){  
        //搜索  
        var searchObjRecs = Ext.data.Record.create([  
           {name: 'formSortUuid', mapping: 'formSortUuid'},   
           {name: 'sortName', mapping: 'sortName'},  
           {name: 'description', mapping: 'description'}  
        ]);  
          
        var searchObjSm = new Ext.grid.CheckboxSelectionModel({header : '' ,singleSelect: true});  
        var searchObjStore = new Ext.data.Store({  
                url : this.contextPath+'/formsort.do?method=getFormSortDatas',  
                autoLoad : false ,  
                reader: new Ext.data.JsonReader(  
                    {  
                       totalProperty: "total",  
                       root: 'data',  
                       id: 'formSortUuid'  
                   },searchObjRecs )  
                  
         });  
         /* 
         var pagingBar = new Ext.PagingToolbar({ 
            pageSize: rowLimit_1, 
            store: searchObjStore, 
            displayInfo: true, 
            displayMsg: '总数: {2}', 
            emptyMsg: '没有数据'       
        }); 
        */  
          
        var searchObjGrid = new Ext.grid.GridPanel({  
                id: 'searchObjGridId',  
                store: searchObjStore,  
                height : 202 ,  
                autoScroll : true ,  
                cm: new Ext.grid.ColumnModel([  
                    searchObjSm,  
                    {header: "编号", width: 100, dataIndex: 'formSortUuid', sortable: true,hidden: true},  
                    {header: "名称", width: 105, dataIndex: 'sortName', sortable: true} ,  
                    {header: "描述", width: 105, dataIndex: 'description', sortable: true}   
                ]),  
                tbar : [  
                    {  
                        text :'添加',  
                        handler : this.createRecord.createDelegate(this)  
                    },'-',{  
                        text :'修改',  
                        handler : this.updateRecord.createDelegate(this)  
                    },'-',{  
                        text :'删除',  
                        handler : this.delteRecord.createDelegate(this)  
                    }  
                ] ,  
                frame: false,  
                loadMask:{msg:"数据加载中...."},  
                sm:searchObjSm   
        });  
          
        return searchObjGrid ;  
    } ,  
    //新建  
    createRecord : function(){  
        this.getWindow().show();  
        this.getWindow().setTitle('新建表单类别');  
        this.getForm().baseParams = {  
            create : true   
        } ;  
    } ,  
    //修改  
    updateRecord : function(){  
        var r = this.getGridSeleted();  
        if(r){  
            this.getWindow().show();  
            this.getWindow().setTitle('修改表单类别');  
            this.getForm().baseParams = {  
                create : false   
            } ;  
            this.getForm().loadRecord(r);  
        }  
    } ,  
    //删除记录   
    delteRecord: function(){  
        var sort = this.protectId ? this.protectId : 'temp' ;  
        var rec = this.getGridSeleted();  
        if(rec){  
            Ext.Msg.confirm('提示','确认删除<b>'+rec.get('sortName')+'</b>吗？',function(btn){  
                if(btn == 'yes'){  
                    if(rec.get('formSortUuid') == sort){  
                        Ext.Msg.alert('提示','<b>'+rec.get('sortName')+'</b>是系统默认类别不能删除！');  
                    }else{  
                        Ext.Ajax.request({  
                            url : this.contextPath+'/formsort.do?method=delFormSort',  
                            params : {sortId : rec.get('formSortUuid')} ,     
                            scope : this ,  
                            callback :function(options ,success ,response ){  
                                if(success){  
                                    var text = response.responseText ;  
                                    if(text == '1'){  
                                        Ext.Msg.alert('提示','删除成功！',function(btn){  
                                            if(btn == 'ok'){  
                                                this.grid.getSelectionModel().clearSelections();   
                                                this.grid.getStore().reload();  
                                            }  
                                        },this);  
                                    }else if(text == '2'){  
                                        Ext.Msg.alert('提示','<b>'+rec.get('sortName')+'</b>已经被业务对象使用不能进行删除！');  
                                    }else{  
                                        Ext.Msg.alert('提示','删除数据失败！');  
                                    }  
                                }else{  
                                    Ext.Msg.alert('提示','删除数据失败！');  
                                }  
                            }  
                        });  
                    }  
                }  
            },this)  
        }  
    },  
      
    createForm : function(){  
        var form = new Ext.form.FormPanel({  
                frame : true ,  
                defaultType : 'textfield' ,  
                buttonAlign : 'center' ,  
                labelAlign : 'right' ,  
                labelWidth : 70 ,  
                items : [  
                    {  
                        fieldLabel : 'id' ,  
                        xtype : 'hidden',  
                        name : 'formSortUuid'  
                    },  
                    {  
                        fieldLabel : '名称' ,  
                        name : 'sortName'  
                    },{  
                        fieldLabel : '描述' ,  
                        xtype : 'textarea' ,  
                        name : 'description'  
                    }  
                ] ,  
                buttons : [  
                    {  
                        text : '确定' ,  
                        scope : this ,  
                        handler : function(){  
                            form.getForm().submit({  
                                    url: this.contextPath+'/formsort.do?method=saveOrUpdateFormSort',  
                                    waitTitle : '请等待' ,  
                                    waitMsg: '正在提交中',  
                                    scope : this ,  
                                    success:function(form,action){  
                                        this.getForm().reset();  
                                        this.grid.getSelectionModel().clearSelections();   
                                        this.grid.getStore().reload();  
                                        this.getWindow().hide();  
                                    },  
                                    failure:function(form,action){  
                                        Ext.Msg.alert('提示','保存失败！');  
                                    }  
                           });  
                        }  
                          
                    } , {  
                        text : '取消' ,  
                        scope : this ,  
                        handler : function(){  
                            this.getForm().reset();  
                            this.getWindow().hide();  
                        }  
                    }     
                ]  
          
        });  
  
        return form ;  
    } ,  
      
    getForm : function(){  
        var form = this.getFormPanel().getForm();  
        return form ;  
    } ,  
      
    getFormPanel : function(){  
        if(!this.gridForm){  
            this.gridForm = this.createForm();  
        }   
        return this.gridForm ;  
    } ,  
      
    createWindow : function(){  
        var form = this.getFormPanel();  
        var win = new Ext.Window({  
                title : 'info' ,  
                closeAction : 'hide' ,  
                width : 300 ,  
                height : 180 ,  
                modal : true ,  
                items : [form]  
              
        });  
        return win ;  
    },  
      
    getWindow : function(){  
        if(!this.gridWindow){  
            this.gridWindow = this.createWindow();  
        }   
        return this.gridWindow ;  
    } ,  
      
      
    //取到grid选择的记录  
    getGridSeleted : function(){  
        var sm = this.grid.getSelectionModel();  
          
        if(sm.hasSelection()){  
            return sm.getSelected() ;  
        }else{  
            Ext.Msg.alert('提示','请选择一条记录！');  
            return null ;  
        }  
    }   
  
})