iOS开发--数组

1.sortedArrayUsingSelector

（按Key值大小对NSDictionary排序）

NSMutableArray *array = [NSMutableArray arrayWithObjects:
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj0", [NSNumber numberWithInt:0], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj5", [NSNumber numberWithInt:5], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj2", [NSNumber numberWithInt:2], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj3", [NSNumber numberWithInt:3], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj1", [NSNumber numberWithInt:1], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj4", [NSNumber numberWithInt:4], nil], nil];

NSArray *resultArray = [array sortedArrayUsingSelector:@selector(compare:)];

因为NSDictionary没有compare的排序比较方法，所以需要我们自己写一个

- (NSComparisonResult)compare: (NSDictionary *)otherDictionary
{
    NSDictionary *tempDictionary = (NSDictionary *)self;

    NSNumber *number1 = [[tempDictionary allKeys] objectAtIndex:0];
    NSNumber *number2 = [[otherDictionary allKeys] objectAtIndex:0];

    NSComparisonResult result = [number1 compare:number2];

    return result == NSOrderedDescending; // 升序
//    return result == NSOrderedAscending;  // 降序
}

2.sortedArrayUsingComparator

    NSMutableArray *array = [NSMutableArray arrayWithObjects:
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj0", [NSNumber numberWithInt:0], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj5", [NSNumber numberWithInt:5], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj2", [NSNumber numberWithInt:2], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj3", [NSNumber numberWithInt:3], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj1", [NSNumber numberWithInt:1], nil],
                             [NSDictionary dictionaryWithObjectsAndKeys:@"Obj4", [NSNumber numberWithInt:4], nil], nil];

//    NSArray *resultArray = [array sortedArrayUsingSelector:@selector(compare:)];

    NSArray *resultArray = [array sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {

        NSNumber *number1 = [[obj1 allKeys] objectAtIndex:0];
        NSNumber *number2 = [[obj2 allKeys] objectAtIndex:0];

        NSComparisonResult result = [number1 compare:number2];

        return result == NSOrderedDescending; // 升序
//        return result == NSOrderedAscending;  // 降序
    }];

3.sortedArrayUsingDescriptors & sortUsingDescriptors

前者带返回值，是NSArray的方法，排好序的数组是返回值中的数组；

后者不带返回值，是NSMutableArray的方法，是对当前数组自己排序

接下来根据一个对象的属性，排列这个对象

.h
@interface Person : NSObject
{
    NSString  *_name;

    NSInteger  _age;
}
@property (nonatomic, retain) NSString  *name;
@property (nonatomic, assign) NSInteger  age;
@end

.m
@implementation Person
@synthesize name = _name;
@synthesize age  = _age;

- (void)dealloc
{
    [_name release];

    [super dealloc];
}

@end

排序方法的实现

    Person *person1 = [[Person alloc] init];
    [person1 setName:@"ABC"];
    [person1 setAge:24];

    Person *person2 = [[Person alloc] init];
    [person2 setName:@"ACB"];
    [person2 setAge:22];

    Person *person3 = [[Person alloc] init];
    [person3 setName:@"ABD"];
    [person3 setAge:33];

    NSMutableArray *array = [NSMutableArray arrayWithObjects:person1, person2, person3, nil];
    [person1 release];
    [person2 release];
    [person3 release];
    //这里类似KVO的读取属性的方法，直接从字符串读取对象属性，注意不要写错
    NSSortDescriptor *sortDescriptor = [NSSortDescriptor sortDescriptorWithKey:@"_age" ascending:YES];
    //这个数组保存的是排序好的对象
    NSArray *tempArray = [array sortedArrayUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];

    for(NSInteger i = 0; i < [tempArray count]; i++)
    {
        NSLog(@"%@--------%d\n", [[tempArray objectAtIndex:i] name], [[tempArray objectAtIndex:i] age]);
    }
//下面是可变数组的方法
//    [array sortUsingDescriptors:[NSArray arrayWithObject:sortDescriptor]];
//
//    for(NSInteger i = 0; i < [array count]; i++)
//    {
//        NSLog(@"%@--------%d\n", [[array objectAtIndex:i] name], [[array objectAtIndex:i] age]);
//    }

NSSortDescriptor *sortDescriptor1 = [NSSortDescriptorsortDescriptorWithKey:@"_age"ascending:YES];

NSSortDescriptor *sortDescriptor2 = [NSSortDescriptorsortDescriptorWithKey:@"_name"ascending:YES];

NSArray *tempArray = [array sortedArrayUsingDescriptors:[NSArrayarrayWithObjects:sortDescriptor1, sortDescriptor2, nil]];

这里的NSArray中的第一元素表示首先按照这个元素的升序或者降序进行排序,对于有重复项的，再按照第二元素进行排序，依次进行类推