角度条件只读/禁用输入字段

我有一个带有输入字段的表,我正在用模型值填充这些字段,我想对这些填充的字段应用readonly/disable。当我单击addrow时,我将空行添加到表中。添加到表中的空行必须是可编辑的。我找不到只对已填充的表单元格应用只读/禁用的逻辑。

HTML格式

<table>
<thead>
    <th> Name </th>
    <th> Age </th>
    <th> Url </th>
    <th> Gender </th>
    <th> Image </th>
    <th> Keywords </th>
</thead>
<tbody>
    <tr *ngFor="let data of userList; let $index = index">
        <td> <input class="form-control" type="text" id="userListName"[(ngModel)]="userList[$index].name"
            name="userListName{{$index}}" [readonly]="userList[$index].name.length"/></td>
        <td> <input class="form-control" type="text" id="userListAge" [(ngModel)]="userList[$index].age"
            name="userListAge{{$index}}" readonly/></td>
        <td><input class="form-control" type="text" id="userListUrl" [(ngModel)]="userList[$index].url" name="userListUrl{{$index}}" readonly/></td>
        <td> <input class="form-control" type="text" id="userListGender" [(ngModel)]="userList[$index].gender"
            name="userListGender{{$index}}" readonly/></td>

        <td> <input class="form-control" type="text" id="userListImage" [(ngModel)]="userList[$index].image"
            name="userListImage{{$index}}"  readonly/>
        </td>
        <td> <input class="form-control" type="text" id="userListKeywords" [(ngModel)]="userList[$index].keywords"
            name="userListKeywords{{$index}}" readonly/></td>
      </tr>
     </tbody>

 <button (click) ="addRow()"> Add Row </button>
 </table>

组成部分:

 import { Component, OnInit } from '@angular/core';

 @Component({
 selector: 'my-app',
 templateUrl: './app.component.html',
 styleUrls: ['./app.component.css']
 })
 export class AppComponent {

 userList: userModel[] = [];

jsonUser = [
{
name: 'abc',
age: 17,
url: "a.com",
gender: "F",
image: "i-ocion.png",
keywords: "blah"
}, 
{
name: 'cde',
age: 18,
url: "cde.com",
gender: "F",
image: "i-oddcion.png",
keywords: "blahhh"
}, 
{
name: 'efg',
age: 19,
url: "efg.com",
gender: "F",
image: "i-ocfffion.png",
keywords: "blahhhhhhh"
}
]
ngOnInit() {
this.userList = this.jsonUser;
}

addRow() {
this.userList.push(new userModel);
}
}

export class userModel {
name: string;
age: number;
url: any;
gender: string;
image: string;
keywords: string;
}

Demo