typescript 初始化对象数组 - Angular
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Initializing array of objects - Angular
提问by Mario
I have an array of objects and when I try to access to it, I get an error saying:
我有一个对象数组，当我尝试访问它时，我收到一条错误消息：
TypeError: Cannot set property 'ID' of undefined
类型错误：无法设置未定义的属性“ID”
My code is the following:
我的代码如下：
export class Carimplements OnInit {
pieces: Piece[] = [];
test(pos){
this.pieces[pos].ID = "test";
}
}
being Piece an object
成为一个对象
export class Piece{
ID: string;
doors: string;
}
I call to test(pos)from the HTML with a valid position.
我test(pos)从具有有效位置的 HTML调用。
I guess that I am trying to access to the position X of an array that has not been initialized. How could I do it? Is it possible to create a constructor?
我想我正在尝试访问尚未初始化的数组的位置 X。我怎么能做到？是否可以创建构造函数？
回答by martin
Correct syntax for defining array types in TypeScript is this:
pieces: Piece[] = [];The error is a runtime error. When you run your app you have an empty array
pieces(but the variable still initialized with[]) but you calltest(whatever)which tries to access an array elementwhateverthat doesn't exist.You can do for example this:
pieces: Piece[] = [{ ID: '1', doors: 'foo' }];and then test this method with
test(0).
在 TypeScript 中定义数组类型的正确语法是这样的：
pieces: Piece[] = [];该错误是运行时错误。当你运行你的应用程序时，你有一个空数组
pieces（但变量仍然用 初始化[]）但是你调用test(whatever)它试图访问一个whatever不存在的数组元素。例如，您可以这样做：
pieces: Piece[] = [{ ID: '1', doors: 'foo' }];然后使用
test(0).
回答by Ekansh Rastogi
You can try the following method
你可以试试下面的方法
test(pos){
if(pos < this.pieces.length)
this.pieces[pos].ID = "test";
else
// throw error
}
回答by TLP
How about this?
这个怎么样？
export class Carimplements OnInit {
pieces: Piece[] = [];
test(pos){
this.pieces[pos] = {ID: "test"};
}
}
回答by Shashidhar Mayannavar
let pieces: Piece[] = [];
//initialize object before assigning value
test(pos){
this.pieces[pos] = new Piece();
this.pieces[pos].ID = "test";
}
