single return + helper

gistfile1.m

- (void)setError:(NSError **)error withOSStatus:(OSStatus)status
{
    if (error != NULL) {
        *error = [NSError errorWithDomain:NSOSStatusErrorDomain code:status userInfo:nil];
    }
}

- (BOOL)play:(NSError **)error;
{
    NSAssert(_graph == NULL, @"Graph is already started");

    OSStatus status;
    
    BOOL result = YES;
    status = NewAUGraph(&_graph);
    if (status == noErr) {
        status = [self addOutputNode];
        if (status == noErr) {
            status = [self addConverterNode];
            if (status == noErr) {
                status = AUGraphConnectNodeInput(_graph, _converterNode, 0, _outputNode, 0);
                if (status == noErr) {
                    status = AUGraphConnectNodeInput(_graph, _converterNode, 0, _outputNode, 0);
                    if (status == noErr) {
                        status = AUGraphOpen(_graph);
                        if (status == noErr) {
                            [self setupDataFormat];
                            status = [self setDataFormatOfConverterAudioUnit];
                            if (status == noErr) {
                                status = [self setMaximumFramesPerSlice];
                                if (status == noErr) {
                                    status = [self setRenderCallbackOfConverterNode];
                                    if (status == noErr) {
                                        status = AUGraphInitialize(_graph);
                                        if (status == noErr) {
                                            A440SineWaveGeneratorInitWithFrequency(&_sineWaveGenerator, 440.0);
                                            status = AUGraphStart(_graph);
                                            if (status != noErr) {
                                                DisposeAUGraph(_graph);
                                                [self setError:error withOSStatus:status];
                                                result = NO;
                                            }
                                        } else {
                                            DisposeAUGraph(_graph);
                                            [self setError:error withOSStatus:status];
                                            result = NO;
                                        }
                                    } else {
                                        DisposeAUGraph(_graph);
                                        [self setError:error withOSStatus:status];
                                        result = NO;
                                    }
                                } else {
                                    DisposeAUGraph(_graph);
                                    [self setError:error withOSStatus:status];
                                    result = NO;
                                }
                            } else {
                                DisposeAUGraph(_graph);
                                [self setError:error withOSStatus:status];
                                result = NO;
                            }
                        } else {
                            DisposeAUGraph(_graph);
                            [self setError:error withOSStatus:status];
                            result = NO;
                        }
                    } else {
                        DisposeAUGraph(_graph);
                        [self setError:error withOSStatus:status];
                        result = NO;
                    }
                } else {
                    DisposeAUGraph(_graph);
                    [self setError:error withOSStatus:status];
                    result = NO;
                }
            } else {
                DisposeAUGraph(_graph);
                [self setError:error withOSStatus:status];
                result = NO;
            }
        } else {
            DisposeAUGraph(_graph);
            [self setError:error withOSStatus:status];
            result = NO;
        }
    } else {
        [self setError:error withOSStatus:status];
        result = NO;
    }
    
    return result;
}