我正在尝试使用async/await,但await没有返回。
这是带有await的异步函数。
async _checkEmailDuplication() {
try {
console.log('Check Email Duplication is called');
let res = await MyNetwork.checkEmail(this.state.email);
console.log('Check email return value: ' + res);
if (res === 0) {
console.log('Available Email');
return false;
}
else {
console.log('Email Duplication Check Error');
return true;
}
}
catch (e) {
console.error('Check Email Call Error', e.message);
return true;
}
console.log('What happened?');
return true;
}
正在调用checkEmail函数,这里是检查Email函数定义
export type EmailCheckResponse = { ret?: number };
class Network {
constructor() {
this._network = NativeModules.NetworkService;
}
checkEmail = (email: string): Promise<EmailCheckResponse> => {
console.log('Network CheckEmail is called');
return this._network.checkEmail(email);
}
}
这是react-native模块并尝试使用iOS中的Nativemodules。
这是 Objective-C Native 模块导出部分。
RCT_EXPORT_METHOD(checkEmail:(NSString *)email
resolver:(RCTPromiseResolveBlock)resolve
rejecter:(RCTPromiseRejectBlock)reject)
{
@autoreleasepool {
[GRPCCall useInsecureConnectionsForHost:kHostAddress];
AccountService *client = [[AccountService alloc] initWithHost:kHostAddress];
EmailCheckRequest *request = [EmailCheckRequest message];
request.email = email;
NSLog(@"Requested Email: %@\n", request.email);
[client checkEmailWithRequest:request handler:^(EmailCheckResponse *response, NSError *error) {
NSLog(@"Email Check result: %d\n", response.ret);
}];
}
}
问题是调用checkEmail后,卡住了。没有返回。
日志说
2017-07-16 16:01:29.355 [info][tid:com.facebook.React.JavaScript] 检查电子邮件重复被调用 2017-07-16 16:01:29.356 [info][tid:com.facebook.React.JavaScript] 网络 CheckEmail 被调用 2017-07-16 16:01:29.364 [50446:3725293] 请求的电子邮件:xxx@xxx.com 2017-07-16 16:01:29.384 [50446:3725170] 电子邮件检查结果:0
看来 Objective-C 模块已成功调用,但没有返回。调用await checkEmail后,没有任何反应。
有人可以告诉我的代码有什么问题吗? =(
最佳答案
我可以从你的React native 模块实现中看到,你忘记调用resolve
和reject
方法,这对于工作 promise 的工作方式至关重要。
[client checkEmailWithRequest:request handler:^(EmailCheckResponse *response, NSError *error) {
NSLog(@"Email Check result: %d\n", response.ret);
if(response){
resolve(response);
}else{
reject(@"no_events", @"There were no events", error);
}
}
];
希望这对您有帮助。
关于JavaScript : Never returns from await,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/45126086/