javascript - angular2 ngIf 真或假条件

Question

谁能帮我解决这个 ngIf 条件，我试图在 key 不存在时隐藏注销，并在 localStorage 中存在时显示它。我对 ngIf 中的多个条件感到困惑，但检查是正确的。

此检查用作指令。

checkSession() {
  var checkKey = localStorage.getItem('sessionKey');
  if(checkKey == null){
      var showLogout = false;
      console.log('null key: ', checkKey);
  } else {
      showLogout = true;
      //this check will only be available once the user is logged in
      console.log('key exist: ' checkKey);
  }

}

HTML

 <a (click)="logout()" title="Logout" *ngIf="showLogout || (!showLogout && !showLogout)">
    <i class="fa fa-sign-out fa-2x" aria-hidden="true" ></i>
 </a>

Answer 1

看来你想要的是

export class MyComponent {

  /// other stuff

  showLogout:boolean = false;

  checkSession() {
    var checkKey = localStorage.getItem('sessionKey');
    if(checkKey == null){
        this.showLogout = false; // changed
        console.log('null key: ', checkKey);
    } else {
        this.showLogout = true; // changed
        //this check will only be available once the user is logged in
        console.log('key exist: ' checkKey);
    }
  }
}

局部变量在模板中不可用。该模板只能直接访问组件类的顶级属性和方法。