Question

我想使用离子样品应用程序来构建Web应用程序。有一部分示例代码是用打字稿编写的。我不明白的代码的含义这个[f] =字段[f] 您能否解释一下此代码的含义？

此ts文件的完整代码为：

  /**
 * A generic model that our Master-Detail pages list, create, and delete.
 *
 * Change "Item" to the noun your app will use. For example, a "Contact," or 
 a
 * "Customer," or a "Animal," or something like that.
 *
 * The Items service manages creating instances of Item, so go ahead and 
rename
 * that something that fits your app as well.
 */
export class Item {

  constructor(fields: any) {
    // Quick and dirty extend/assign fields to this model
    for (const f in fields) {
      // @ts-ignore
      this[f] = fields[f];
    }
  }

 }

export interface Item {
  [prop: string]: any;
}

Answer 1

您正在查看动态属性访问器。假设“字段”为{first: 1, second: 2}，则代码等同于：

this.first = fields.first this.second = fields.second

因此，简而言之，它会将字段的所有可枚举属性分配给它。

MDN web docs: Property accessor

Answer 2

将其视为通用构造函数。它的作用是在函数范围内迭代别名为“字段”的对象的成员，并将值分配给要创建的对象“ this”。例如，如果传递的对象是：

var fields= {mem1: 1, mem2: 'marios'};

the code would then

for (const f in fields) {
      this[f] = fields[f];
      // 1st iteration would be
      // this[mem1] =  fields[mem1]; -> this[mem1] will create the property to the new object
      // fields[mem1] will read the value, so it created the prop and copies the value 
    }

Answer 3

这是属性访问的括号符号。您可以了解有关MDN here

的更多信息

打字稿中syntax []的含义是什么

3 个答案: