从xcode 5.0移动到5.1时，在GPUImage Library中出现以下错误。在google上搜索后我发现我需要像这样发送int [NSNumber numberWithInt：number]，但问题是我没有控制在下面给出的代码中传递给sortedArrayUsingComparator的值。
错误日志：
不兼容的块指针类型将'int（^）（__ strong id，_ strong id）'发送到'NSComparator'类型的参数（又名'NSComparisonResult（^）（ _strong id，__strong id） “）
此行出错：NSArray * sortedPoints = [points sortedArrayUsingComparator：^（id a，id b）{
- (id) initWithCurveFile:(NSString*)curveFile
{
self = [super init];
if (self != nil)
{
NSString *bundleCurvePath = [[[NSBundle mainBundle] resourcePath] stringByAppendingPathComponent: curveFile];
NSFileHandle* file = [NSFileHandle fileHandleForReadingAtPath: bundleCurvePath];
if (file == nil)
{
NSLog(@"Failed to open file");
return self;
}
NSData *databuffer;
// 2 bytes, Version ( = 1 or = 4)
databuffer = [file readDataOfLength: 2];
version = CFSwapInt16BigToHost(*(int*)([databuffer bytes]));
// 2 bytes, Count of curves in the file.
[file seekToFileOffset:2];
databuffer = [file readDataOfLength:2];
totalCurves = CFSwapInt16BigToHost(*(int*)([databuffer bytes]));
NSMutableArray *curves = [NSMutableArray new];
float pointRate = (1.0 / 255);
// The following is the data for each curve specified by count above
for (NSInteger x = 0; x<totalCurves; x++)
{
// 2 bytes, Count of points in the curve (short integer from 2...19)
databuffer = [file readDataOfLength:2];
short pointCount = CFSwapInt16BigToHost(*(int*)([databuffer bytes]));
NSMutableArray *points = [NSMutableArray new];
// point count * 4
// Curve points. Each curve point is a pair of short integers where
// the first number is the output value (vertical coordinate on the
// Curves dialog graph) and the second is the input value. All coordinates have range 0 to 255.
for (NSInteger y = 0; y<pointCount; y++)
{
databuffer = [file readDataOfLength:2];
short y = CFSwapInt16BigToHost(*(int*)([databuffer bytes]));
databuffer = [file readDataOfLength:2];
short x = CFSwapInt16BigToHost(*(int*)([databuffer bytes]));
[points addObject:[NSValue valueWithCGSize:CGSizeMake(x * pointRate, y * pointRate)]];
}
[curves addObject:points];
}
[file closeFile];
rgbCompositeCurvePoints = [curves objectAtIndex:0];
redCurvePoints = [curves objectAtIndex:1];
greenCurvePoints = [curves objectAtIndex:2];
blueCurvePoints = [curves objectAtIndex:3];
}
return self;
}
- (NSArray *)getPreparedSplineCurve:(NSArray *)points
{
if (points && [points count] > 0)
{
// Sort the array.
NSArray *sortedPoints = [points sortedArrayUsingComparator:^(id a, id b) {
float x1 = [(NSValue *)a CGPointValue].x;
float x2 = [(NSValue *)b CGPointValue].x;
return x1 > x2;
}];
// Convert from (0, 1) to (0, 255).
NSMutableArray *convertedPoints = [NSMutableArray arrayWithCapacity:[sortedPoints count]];
for (int i=0; i<[points count]; i++){
CGPoint point = [[sortedPoints objectAtIndex:i] CGPointValue];
point.x = point.x * 255;
point.y = point.y * 255;
[convertedPoints addObject:[NSValue valueWithCGPoint:point]];
}
NSMutableArray *splinePoints = [self splineCurve:convertedPoints];
// If we have a first point like (0.3, 0) we'll be missing some points at the beginning
// that should be 0.
CGPoint firstSplinePoint = [[splinePoints objectAtIndex:0] CGPointValue];
if (firstSplinePoint.x > 0) {
for (int i=0; i <=firstSplinePoint.x; i++) {
CGPoint newCGPoint = CGPointMake(0, 0);
[splinePoints insertObject:[NSValue valueWithCGPoint:newCGPoint] atIndex:0];
}
}
// Prepare the spline points.
NSMutableArray *preparedSplinePoints = [NSMutableArray arrayWithCapacity:[splinePoints count]];
for (int i=0; i<[splinePoints count]; i++)
{
CGPoint newPoint = [[splinePoints objectAtIndex:i] CGPointValue];
CGPoint origPoint = CGPointMake(newPoint.x, newPoint.x);
float distance = sqrt(pow((origPoint.x - newPoint.x), 2.0) + pow((origPoint.y - newPoint.y), 2.0));
if (origPoint.y > newPoint.y)
{
distance = -distance;
}
[preparedSplinePoints addObject:[NSNumber numberWithFloat:distance]];
}
return preparedSplinePoints;
}
return nil;
}
答案 0 :(得分：5)
比较块必须返回NSComparisonResult，即
NSOrderedAscending，NSOrderedSame或NSOrderedDescending（a.k.a。-1，0，+1），
取决于第一个元素是否小于，等于或大于第二个元素。）
返回x1 > x2不符合此要求，编译器会抱怨因为
它从最后一个语句“推断”返回类型为int。
要解决此问题，您可以
-1，0或+1，和 NSComparisonResult
让编译器开心。您还可以通过将块参数声明为，来略微简化代码
NSValue *。
NSArray *sortedPoints = [points sortedArrayUsingComparator:^NSComparisonResult(NSValue *a, NSValue *b) {
float x1 = [a CGPointValue].x;
float x2 = [b CGPointValue].x;
return (x1 > x2) - (x2 > x1); // -1, 0, or +1
}];
答案 1 :(得分：0)
您对CFSwapInt16BigToHost的调用是错误的。你是否认为将32位int传递给16位中交换字节的函数是不对的？从只包含两个字节的NSData对象中读取4个字节是不是正确的？
您收到错误消息。我觉得很清楚。它告诉您预期的参数，以及您给出的参数。当你收到一条错误信息时，不要让你的大脑陷入困境并思考＆＃34;哦，天哪，代码仙女反对我，我需要一些我不知道的魔法＆＃34; 。您需要思考：＆＃34;我的代码中存在错误。这是哪个错误？ ＆＃34;在这种情况下，很明显。错误消息告诉您。您需要一个块返回NSComparisonResult。
下一步应该是寻找NSComparisonResult的定义。在那里你会发现你应该返回三个可能值中的一个，而你的函数只返回两个可能值中的一个。因此，如果您只是编译它，它将无法正确排序。
你可能已经使用了代码完成功能，它会填充具有所有正确类型的块的骨架，因此你不会有机会在第一时间出错。您还应该找到Apple的块文档，并了解如何确定返回类型。阅读文档是学习和成为更好的程序员的一种非常好的方式。
答案 2 :(得分：0)
我得到了同样的错误。解决方案正如其他人所建议的那样，我试图用一种简单的方式来解决这个问题：
更改块：
^(id a, id b)
于：
^NSComparisonResult(id a, id b)
那你就定了。