数组排序

        //1.使用sortedArrayUsingSelector
        //也是最简单的排序方式
        //数组是按照你存入元素的顺序存储的
        
        NSArray * array = @[@"b",@"d",@"a",@"z"];
        NSLog(@"排序前 array %@",array);
        
        array = [array sortedArrayUsingSelector:@selector(compare:)];
//        NSArray * array1 = [array sortedArrayUsingSelector:@selector(compare:)];
        NSLog(@"排序后 array %@",array);
        
        //2.使用block方式排序
        NSArray * array2 = @[@"z",@"4",@"b",@"3",@"x"];
        
        NSLog(@"array2 排序前 %@",array2);
        array2 = [array2 sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
            
            /*
            NSComparisonResult retuslt = [obj1 compare:obj2];
            
            return retuslt;
             */
            //obj1 compare obj2 就是正序排序
//            return [obj1 compare:obj2];
            //obj2 compare obj1 就是倒序排序
            return [obj2 compare:obj1];
            
        }];
        NSLog(@"array2 排序后 %@",array2);
        
       
        Person * p1 = [[Person alloc] initWithName:@"xiaozhe" andAge:20 andYear:@"1990"];
        Person * p2 = [[Person alloc] initWithName:@"alex" andAge:18 andYear:@"2990"];
        Person * p3 = [[Person alloc] initWithName:@"merry" andAge:25 andYear:@"1890"];
        
        NSArray * array3 = @[p1,p2,p3];
        NSLog(@"array3 排序前 %@",array3);
        
        //3.使用 给数组排序
        //如果你向给你自己定义的对象排序,必须根据某一个属性来排序,
        //sortDescriptorWithKey 参数要的就是你对象中,要依据哪个属性来排序,你就把哪个属性的名字当成key传入
        //ascending YES表示正序 NO表示倒叙
        NSSortDescriptor * d1 = [NSSortDescriptor sortDescriptorWithKey:@"age" ascending:NO];
        NSSortDescriptor * d2 = [NSSortDescriptor sortDescriptorWithKey:@"year" ascending:NO];
        
        //如果你要使用多个属性进行排序,默认在前面的NSSortDescriptor优先级比较高
        NSArray * descripts = @[d2,d1];
        
        array3 = [array3 sortedArrayUsingDescriptors:descripts];
        
        NSLog(@"array 3 排序后  %@",array3);
        
        
        //4.

        NSArray * array4 = @[p1,p2,p3];
        NSLog(@"array4 排序前 %@",array4);
        array4 = [array4 sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
            
            Person * p1 = obj1;
            Person * p2 = obj2;
            
            //year
            return [p1.year compare:p2.year];
            
            
        }];
        NSLog(@"array4 排序后 %@",array4);

#import <Foundation/Foundation.h>

@interface Person : NSObject

@property (nonatomic,assign) int age;
@property (nonatomic,strong) NSString * name;
@property (nonatomic,strong) NSString * year;

- (id)initWithName:(NSString *)name  andAge:(int)age andYear:(NSString *)year;
//+ (id)personWithName:(NSString *)name  andAge:(int)age andYear:(NSString *)year;

@end

#import "Person.h"

@implementation Person

- (id)initWithName:(NSString *)name  andAge:(int)age andYear:(NSString *)year
{
    if (self = [super init])
    {
        _name = name;
        _age = age;
        _year = year;
        
    }
    return self;
}

- (NSString *)description
{
    return [NSString stringWithFormat:@"name %@ age %d year %@",_name,_age,_year];
}

@end