Firebase和Ionic 2，将用户UID添加到数据库时

Question

我试图在firebase函数之外传递变量 ownerID，但是即使函数在函数之外声明了变量，它也会在关闭函数后未定义。我该如何解决？

addBook():void {
var ownerID
let prompt = this.alertCtrl.create({
  title: 'Adicionar Livros',
  message: 'Adicione as informações do livro',
  inputs: [
    {
      name: 'title',
      placeholder: "Título do Livro"
    },
    {
      name: 'author',
      placeholder: "Nome do Autor"
    },
    {
      name: 'description',
      placeholder: "Descrição do Livro"
    },
    {
      name: 'city',
      placeholder: "Sua Cidade"
    },
  ],
  buttons: [
    {
      text: "Cancelar",
      handler: data => {
        console.log("cancel clicked");
      }
    },
    {
      text: "Salvar",
      handler: data => {
        firebase.auth().onAuthStateChanged(function(user) {
          if (user) {
            ownerID = user.uid;
            console.log(ownerID); // this prints fine
          }
        })
          console.log(ownerID) // this is undefined
        this.books.push({
          title: data.title,
          author: data.author,
          description: data.description,
          city: data.city,
          owner: ownerID
        })
      }
    }
  ],
})
prompt.present();
}

Answer 1

如果我没记错的 firebase.auth().onAuthStateChanged返回诺言，所以我认为您需要一个 then()

firebase.auth().onAuthStateChanged(user => {
   if (user) {
      ownerID = user.uid;
   }
}).then(data => {
   console.log(ownerID)
});

onauthstatatechanged

返回非壁炉式firebase.promise包含void