objective-c - 如何内联编写Objective-C块？

我正在尝试使用objective-c块实现二进制搜索。我正在使用函数indexOfObject:inSortedRange:options:usingComparator:。这是一个例子。

// A pile of data.
NSUInteger amount = 900000;
// A number to search for.
NSNumber* number = [NSNumber numberWithInt:724242];

// Create some array.
NSMutableArray* array = [NSMutableArray arrayWithCapacity:amount];
for (NSUInteger i = 0; i < amount; ++i) {;
    [array addObject:[NSNumber numberWithUnsignedInteger:i]];
}
NSTimeInterval start = [NSDate timeIntervalSinceReferenceDate];

// Run binary search.
int index1 = [array indexOfObject:number
                    inSortedRange:NSMakeRange(0, [array count])
                          options:NSBinarySearchingFirstEqual
                  usingComparator:^(id lhs, id rhs) {
                      if ([lhs intValue] < [rhs intValue]) {
                          return (NSComparisonResult)NSOrderedAscending;
                      } else if([lhs intValue] > [rhs intValue]) {
                          return (NSComparisonResult)NSOrderedDescending;
                      }
                      return (NSComparisonResult)NSOrderedSame;
                  }];
NSTimeInterval stop1 = [NSDate timeIntervalSinceReferenceDate];
NSLog(@"Binary: Found index position: %d in %f seconds.", index1, stop1 - start);

// Run normal search.
int index2 = [array indexOfObject:number];
NSTimeInterval stop2 = [NSDate timeIntervalSinceReferenceDate];
NSLog(@"Normal: Found index position: %d in %f seconds.", index2, stop2 - start);

我想知道如何使用外部定义的objective-c块来实现上述功能。这里有两个比较函数。

NSComparisonResult compareNSNumber(id lhs, id rhs) {
    return [lhs intValue] < [rhs intValue] ? NSOrderedAscending : [lhs intValue] > [rhs intValue] ? NSOrderedDescending : NSOrderedSame;
}
NSComparisonResult compareInt(int lhs, int rhs) {
    return lhs < rhs ? NSOrderedAscending : lhs > rhs ? NSOrderedDescending : NSOrderedSame;
}

这些是参照下面的声明编写的，这些声明可以在NSObjCRuntime.h中找到。

enum _NSComparisonResult {NSOrderedAscending = -1, NSOrderedSame, NSOrderedDescending};
typedef NSInteger NSComparisonResult;
typedef NSComparisonResult (^NSComparator)(id obj1, id obj2);

最佳答案

可以将块定义为全局变量，以获得类似于函数的效果。

NSComparisonResult (^globalBlock)(id,id) = ^(id lhs, id rhs) {
    if([lhs intValue] < [rhs intValue]) {
        return (NSComparisonResult)NSOrderedAscending;
    } else if([lhs intValue] > [rhs intValue]) {
        return (NSComparisonResult)NSOrderedDescending;
    }
    return (NSComparisonResult)NSOrderedSame;
};

然后，在进行比较的方法中：

int index1 = [array indexOfObject:number
                    inSortedRange:NSMakeRange(0, [array count])
                          options:NSBinarySearchingFirstEqual
                  usingComparator:globalBlock];

要将块放在头中，供外部使用：

NSComparisonResult (^globalBlock)(id,id);