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Add support for adding a future into a dispatch group #19

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6fb63e3
Add support for adding a future into a dispatch group
Apr 6, 2018
1cbe084
Merge branch 'master' into DispatchGroup
garrettmoon Mar 22, 2019
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7 changes: 7 additions & 0 deletions PINFuture/Classes/PINFuture.h
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,13 @@ NS_ASSUME_NONNULL_BEGIN
*/
- (void)executor:(id<PINExecutor>)executor success:(nullable void(^)(ObjectType value))success failure:(nullable void(^)(NSError *error))failure;

/**
* Enter the given dispatch group now, and
* leave when the future completes. If the future
* is already completed, this method has no effect.
*/
- (void)addToDispatchGroup:(dispatch_group_t)dispatchGroup;

@garrettmoon garrettmoon Mar 22, 2019

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I wonder if this is the best way to expose the composite future feature you're suggesting?

Separately, I think it would be more PINFuture-y to have this in a category and import it below?


@end

NS_ASSUME_NONNULL_END
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42 changes: 35 additions & 7 deletions PINFuture/Classes/PINFuture.m
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,7 @@ @interface PINFuture ()

@property (nonatomic) NSLock *propertyLock;
// TODO(chris): Use PINResult here.
@property (nonatomic) enum PINFutureState state;
@property (nonatomic) PINFutureState state;
@property (nonatomic, nullable) id value;
@property (nonatomic, nullable) NSError *error;
@property (nonatomic, nullable) NSMutableArray<PINFutureCallback *> *callbacks; // If nil, there are no callbacks
Expand Down Expand Up @@ -102,17 +102,35 @@ - (void)executor:(id<PINExecutor>)executor success:(nullable void(^)(id value))s
callback.success = success;
callback.failure = failure;
[self.propertyLock lock];
// Lazily instantiate self.callbacks. Lots of futures will never have any callbacks.
if (self.callbacks == nil) {
self.callbacks = [NSMutableArray new];
}

[self.callbacks addObject:callback];
[self locked_attachCallback:callback];
[self.propertyLock unlock];

[self tryFlushCallbacks];
}

- (void)addToDispatchGroup:(dispatch_group_t)dispatchGroup
{
[self.propertyLock lock];
if (self.state == PINFutureStatePending) {
// We're pending. Enter the group now,
// and attach a callback to leave the group
// on completion.
dispatch_group_enter(dispatchGroup);
PINFutureCallback *callback = [[PINFutureCallback alloc] init];
callback.executor = PINExecutor.immediate;
callback.success = ^(__unused id value) {
dispatch_group_leave(dispatchGroup);
};
callback.failure = ^(__unused NSError * error) {
dispatch_group_leave(dispatchGroup);
};
[self locked_attachCallback:callback];
} else {
// nop, we're already finished.
}
[self.propertyLock unlock];
}

#pragma mark - internal

- (void)transitionToState:(PINFutureState)state value:(nullable NSObject *)value error:(nullable NSError *)error
Expand All @@ -130,6 +148,16 @@ - (void)transitionToState:(PINFutureState)state value:(nullable NSObject *)value
[self tryFlushCallbacks];
}

- (void)locked_attachCallback:(PINFutureCallback *)callback
{
// Lazily instantiate self.callbacks. Lots of futures will never have any callbacks.
if (self.callbacks == nil) {
self.callbacks = [NSMutableArray new];
}

[self.callbacks addObject:callback];
}

- (void)tryFlushCallbacks
{
NSArray<PINFutureCallback *> *callbacks;
Expand Down