src/objective-c/RxLibrary/GRXImmediateSingleWriter.m

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#import "GRXImmediateSingleWriter.h"

@implementation GRXImmediateSingleWriter {
  id _value;
  id<GRXWriteable> _writeable;
}

@synthesize state = _state;

- (instancetype)initWithValue:(id)value {
  if (self = [super init]) {
    _value = value;
    _state = GRXWriterStateNotStarted;
  }
  return self;
}

+ (GRXWriter *)writerWithValue:(id)value {
  return [[self alloc] initWithValue:value];
}

- (void)startWithWriteable:(id<GRXWriteable>)writeable {
  _state = GRXWriterStateStarted;
  _writeable = writeable;
  [writeable writeValue:_value];
  [self finish];
}

- (void)finish {
  _state = GRXWriterStateFinished;
  _value = nil;
  id<GRXWriteable> writeable = _writeable;
  _writeable = nil;
  [writeable writesFinishedWithError:nil];
}

// Overwrite the setter to disallow manual state transition. The getter
// of _state is synthesized.
- (void)setState:(GRXWriterState)newState {
  // Manual state transition is not allowed
  return;
}

// Overrides [requestWriter(Transformations):map:] for Protocol Buffers
// encoding.
// We need the return value of this map to be a GRXImmediateSingleWriter but
// the original \a map function returns a new Writer of another type. So we
// need to override this function here.
- (GRXWriter *)map:(id (^)(id))map {
  // Since _value is available when creating the object, we can simply
  // apply the map and store the output.
  _value = map(_value);
  return self;
}

@end