interface JsonResponse {
  version:number;
  outOfStock?: boolean;
  readonly body: string;
  update: (retryTimes: number) => void;
  update2(retryTimes: number):void
}
interface JsonResponse2 { [key: string]: number }

interface JsonResponse {
  (): string;
  toFn: string
}
const fn: JsonResponse = () => {
  return 'str'
}
fn.toFn = 'content'

// 接口扩展接口
interface X { x: number }
interface Point extends X { y: number }
// Point {x:numer;y:number}
// 也可扩展类型别名，同时可扩展多个
type Y = { y: number }
interface Point2 extends X, Y { z: number }
// Point2 {x:numer;y:number;z:number}

interface Legged {
  numberOfLegs: number;
}
interface Legged {
  numberOfLegs: 123;
}
// 报错，numberOfLegs 必须都为 number
// ======= 在namespace 中也是如此
namespace Animals {
  export interface Legged {
    numberOfLegs: number;
  }
}
namespace Animals {
  export interface Legged {
    numberOfHands: number;
  }
}
// 合并为
namespace Animals {
  export interface Legged {
    numberOfLegs: number;
    numberOfHands: number;
  }
}

interface JsonResponse {
  version: number
}
interface JsonResponse {
  /** In bytes */
  payloadSize: number
}

interface APICall<R> {
  data: R
}
// 使用
interface JsonResponse { content: string };
const api: APICall<JsonResponse> = { data: { content: 'xxx' } }
api.data.content

// 意味着要有 status 属性的类型才能使用
interface APICall<R extends { status: number }> {
  data: R
}
// 使用
interface JsonResponse { content: string, status: number };
const api: APICall<JsonResponse> = { data: { content: 'xxx', status: 200 } }
api.data.status

interface Ruler {
  get size(): number | string
  set size(value: number | string)
}
const ruler:Ruler = {
  size: 123
}
ruler.size = 456
ruler.size = '456'
ruler.size  // 类型为 string
// Error
// ruler.size = false

interface Syncable { sync(): void }
class Account implements Syncable {
  sync() { }
}
// 必须实现 sync 方法