HttpOverrides 类 抽象

此类提供了一种覆盖 HttpClient 以使用模拟实现的机制。它应在客户端代码中的另一个类中扩展，并提供用于构建模拟实现的覆盖。此基类的实现默认为实际 HttpClient 实现。例如

// An implementation of the HttpClient interface
class MyHttpClient implements HttpClient {
  MyHttpClient(SecurityContext? c);

  @override
  noSuchMethod(Invocation invocation) {
    // your implementation here
  }
}

void main() {
  HttpOverrides.runZoned(() {
    // Operations will use MyHttpClient instead of the real HttpClient
    // implementation whenever HttpClient is used.
  }, createHttpClient: (SecurityContext? c) => MyHttpClient(c));
}