离子如何让订阅变量到全局变量

Question

我努力按照以下方式使用。您能帮忙吗？

     this.categories=this.menuservice.getChildCategories(this.catId)
    .subscribe(( children: Children[]) => {
      return  this.children = children
      console.log("1st=",children);

   });

   console.log("2nd=",this.categories);