我遇到了Angular2上的模型绑定没有按照我的预期绑定的地方,而且我在确定出错的地方时遇到了问题。
我有一个对象数组如下:
commands = [
{
"id": 2,
"command": "!first",
"action": "This is the first command. You found it!",
"reply": false
},
{
"id": 5,
"command": "!hi",
"action": "Hello, how are you today?",
"reply": true
},
...
];
视图模板如下(为简洁起见,仅显示带有相关Angular2信息的标签):
<form #commandForm="ngForm">
<tr *ngFor="#cmd of commands">
<td *ngIf=" ! isEditingCommand(cmd)">{{ cmd.command }}</td>
<td *ngIf="isEditingCommand(cmd)">
<input type="text" class="form-control" placeholder="!command" required [(ngModel)]="cmd.command" (ngModelChange)="cmd.command=cleanCommand($event)" ngControl="cmd" #cmd="ngForm">
</td>
<td *ngIf=" ! isEditingCommand(cmd)">{{ cmd.action }}</td>
<td *ngIf="isEditingCommand(cmd)">
<textarea class="form-control" rows="1" placeholder="Text to display." required [(ngModel)]="cmd.action" ngControl="action" #action="ngForm"></textarea>
</td>
</tr>
</form>
当isEditingCommand(cmd) === false
时,行显示如下:
当isEditingCommand(cmd) === true
时,这就是我得到的:
我已将cmd
和cmd.command
更改为各种名称,如果command
是Angular2的保留字,则无效。当我在视图中放置{{ cmd | json }}
时,我收到此异常:
EXCEPTION: TypeError: Converting circular structure to JSON in [
{{ cmd | json }}
in CommandComponent@24:199]
遗憾的是,我无法确定这是如何形成圆形结构的。即使通过Chrome Inspector,我也找不到可能是圆形的地方。
为了提供帮助,以下是视图中定义的函数(TypeScript给我带来了问题;我稍后会重构它):
CommandComponent.prototype.cleanCommand = function (value) {
value = value.replace(/[^a-z]+/gi, '');
if (0 >= value.indexOf('!') && '!' !== value.substr(0, 1)) {
value = '!' + value;
}
return value;
};
CommandComponent.prototype.isEditingCommand = function (command) {
if (null === this.currentCommand) {
return false;
}
return this.editFormActive && this.currentCommand.id === command.id;
};
// These are not used by the template shown, but they set values used in the functions.
CommandComponent.prototype.editCommand = function (command) {
this.editFormActive = true;
this.currentCommand = command;
};
CommandComponent.prototype.cancelEditCommand = function () {
this.editFormActive = false;
this.currentCommand = null;
};
环境:
我做错了什么?如果需要更多信息,请告诉我,谢谢!
答案 0 :(得分:2)
我不确定我是否理解你的问题。但是,我只看到一个可能导致一些约束问题的问题。
在这一行:
<input type="text" class="form-control" placeholder="!command" required [(ngModel)]="cmd.command" (ngModelChange)="cmd.command=cleanCommand($event)" ngControl="cmd" #cmd="ngForm">
您重新定义了本地变量cmd
。第一个是*ngFor="#cmd of commands"
。另一个#cmd="ngForm"
。因此,与cmd.command
的绑定将是cmd
ngForm
而不是#cmd of commands
。换句话说,您已将新属性command
添加到ngForm
。
这将解释循环引用问题,因为ngForm
属于NgFormName
,其_parent
引用。