如何使这行代码工作？

Question

  var relative = af.database.object('users/user75ECZOiNtxZwYoezaXmYA9YwPm53', { preserveSnapshot: true });
  relative.subscribe(
    snapshot => {
      this.usedBasicProfile = snapshot;
    }
  );
  console.log(this.usedBasicProfile);  //the value is undefined, how to make this work?

我想要做的是从firebase获取数据，任何人都可以帮助我吗？

Answer 1

您似乎正在使用异步方法，这意味着在执行进入回调处理程序之前，该值不可用。你试过这个吗？

var relative = af.database.object('users/user75ECZOiNtxZwYoezaXmYA9YwPm53', { preserveSnapshot: true });

relative.subscribe(snapshot => {
    this.usedBasicProfile = snapshot;
    console.log(this.usedBasicProfile);
});