- catch
Subscribes to the returned signal when an error occurs.
当error发生时，订阅返回信号
可以理解为捕获信号的error信息
RACSignal *signal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
[subscriber sendNext:@"我是发送的信号"];
[subscriber sendError:[NSError errorWithDomain:@"www.huang"
code:0
userInfo:@{NSLocalizedDescriptionKey:@"错误信息"}]];
return nil;
}];
RACSignal *newSignal = [signal catch:^RACSignal *(NSError *error) {
NSLog(@"%@",error.localizedDescription);
// 注意如果这里使用 [RACSignal return:error] newSignal就不会走error的回调了
return [RACSignal error:error];
}];
[newSignal subscribeNext:^(id x) {
NSLog(@"%@",x);
} error:^(NSError * error) {
NSLog(@"=%@",error.localizedDescription);
}];
***************
打印日志:
我是发送的信号
错误信息
=错误信息
- catchTo
Subscribes to the given signal when an error occurs.
catchTo 与 catch 相同的触发场景，都需要订阅者调用[subscriber sendError]方法时。
RACSignal *signal = [RACSignal createSignal:^RACDisposable *(id<RACSubscriber> subscriber) {
[subscriber sendNext:@"我是发送的信号"];
// error occurs
[subscriber sendError:[NSError errorWithDomain:@"www.huang"
code:0
userInfo:@{NSLocalizedDescriptionKey:@"错误信息"}]];
return nil;
}];
// RACSignal *newSignal = [signal catchTo:[RACSignal return:@(1122)]]; // 走next回调
RACSignal *newSignal = [signal catchTo:[RACSignal error:[NSError errorWithDomain:@"www.huang" code:0 userInfo:@{NSLocalizedDescriptionKey:@"catch的错误信息"}]]]; // 走error回调
[newSignal subscribeNext:^(id x) {
NSLog(@"next:%@",x);
} error:^(NSError *error) {
NSLog(@"error:%@",error.localizedDescription);
}];
***************
打印日志:
next:我是发送的信号
error:catch的错误信息
需要注意的是，当调用catchTo方法时，是可以拦截next回调或error回调的，取决于被catchTo的信号。
- 源码
- (RACSignal *)catch:(RACSignal * (^)(NSError *error))catchBlock {
NSCParameterAssert(catchBlock != NULL);
return [[RACSignal createSignal:^(id<RACSubscriber> subscriber) {
RACSerialDisposable *catchDisposable = [[RACSerialDisposable alloc] init];
RACDisposable *subscriptionDisposable = [self subscribeNext:^(id x) {
[subscriber sendNext:x]; //不会拦截原来的value； 原来的信号变为热信号，新信号被订阅会来到这里
} error:^(NSError *error) {
RACSignal *signal = catchBlock(error); // 外界传入的信号
NSCAssert(signal != nil, @"Expected non-nil signal from catch block on %@", self);
catchDisposable.disposable = [signal subscribe:subscriber];
} completed:^{
[subscriber sendCompleted];
}];
return [RACDisposable disposableWithBlock:^{
[catchDisposable dispose];
[subscriptionDisposable dispose];
}];
}] setNameWithFormat:@"[%@] -catch:", self.name];
}
- (RACSignal *)catchTo:(RACSignal *)signal {
return [[self catch:^(NSError *error) {
return signal; // 传入的信号当做新信号返回，所以订阅新信号的结果决定于传入的信号！
}] setNameWithFormat:@"[%@] -catchTo: %@", self.name, signal];
}
