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NSComparisonResult類:枚舉類型, 來標示比較操作的升降序。其定義如下

typedef NS_ENUM(NSInteger, NSComparisonResult) {NSOrderedAscending = -1L, NSOrderedSame, NSOrderedDescending};

參數(shù)解釋

• NSOrderedAscending

  • The left operand is smaller than the right operand.(左邊的操作對象小于右邊的對象)

• NSOrderedSame

  • The two operands are equal.(左邊的操作對象等于右邊的對象)

• NSOrderedDescending

  • The left operand is greater than the right operand.(左邊的操作對象大于右邊的對象)

NSComparator類:實際上是用一個block對象作比較操作(The arguments to the Block object are two objects to compare. The block returns an NSComparisonResult value to denote the ordering of the two objects)。其定義如下：

typedef NSComparisonResult (^NSComparator)(id obj1, id obj2); 

參數(shù)解釋

• id obj1 與 id obj2

  • 將要做比較的對象。

• block

  • 返回的結(jié)果為NSComparisonResult類型來表示兩個對象的順序

使用范例:

NSArray *sortedArray = [array sortedArrayUsingComparator: ^(id obj1, id obj2) {
 
    if ([obj1 integerValue] > [obj2 integerValue]) {
        return (NSComparisonResult)NSOrderedDescending;
    }
 
    if ([obj1 integerValue] < [obj2 integerValue]) {
        return (NSComparisonResult)NSOrderedAscending;
    }
    return (NSComparisonResult)NSOrderedSame;
}];