PromiseKit "Common Patterns"文档采用 Swift 语言。
如何在 Objective C 中编写重试/轮询代码?
重试/轮询
func attempt<T>(maximumRetryCount: Int = 3, delayBeforeRetry: DispatchTimeInterval = .seconds(2), _ body: @escaping () -> Promise<T>) -> Promise<T> {
var attempts = 0
func attempt() -> Promise<T> {
attempts += 1
return body().recover { error -> Promise<T> in
guard attempts < maximumRetryCount else { throw error }
return after(delayBeforeRetry).then(on: nil, attempt)
}
}
return attempt()
}
attempt(maximumRetryCount: 3) {
flakeyTask(parameters: foo)
}.then {
//…
}.catch { _ in
// we attempted three times but still failed
}
最佳答案
PromiseKit 开发者在 Github 上回答:
- (AnyPromise *) attempt:(NSUInteger) maximumRetryCount delayBeforeRetry:(NSTimeInterval) delay provider:(AnyPromise* (^)()) provide {
__block NSUInteger attempts = 0;
AnyPromise *(^attempt)() = ^{
attempts++;
return provide().catch(^(id error) {
if (attempts >= maximumRetryCount) @throw error;
return PMKAfter(delay).then(attempt);
});
};
return attempt();
}
然后,如果你有这样的方法:
- (AnyPromise *) myPromise {
return [AnyPromise promiseWithResolverBlock:^(PMKResolver resolve) {
...
resolve(nil) / resolve (error);
}];
}
调用它
[self attempt:3 delayBeforeRetry:2 provider:^{ return [self myPromise]; }]
关于ios - PromiseKit:如何在 ObjC 中进行重试/轮询?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/55414224/