集合

• 集合特点：
  1⃣️存储的元素互不相同(若在集合中放入两个相同的元素,会自动过滤掉其中一个)
  2⃣️存储元素是无序的
  3⃣️存储元素必须是对象类型
  4⃣️集合是一种哈希表，运用散列算法，查找集合中的元素比数组速度更快

在iOS中的容器常用有三个：NSArrey \ NSdictionary \ NSSet，这里主要介绍一下NSSet的用法

1. NSSet创建方式

    NSSet *set = [NSSet setWithObjects:@"12",@"牛皮",@"12", nil];
    NSLog(@"set->%@,count->%lu",set,(unsigned long)set.count); //set->12,牛皮  count->2
    
    NSSet *set1 = [[NSSet alloc] initWithObjects:@"1",@"2",@"3",@"4",@"5", nil];
    NSLog(@"set1->%@",set1); //set1->3,1,4,2,5

2. NSSet比较

    NSSet<NSString *> *set1 = [NSSet setWithObjects:@"12",@"Yes",@"56",@"caodan", nil];
    NSSet<NSString *> *set2 = [NSSet setWithObjects:@"bi", @"12",@"Yes", nil];
       
    // 是否子集合
    BOOL isBool = [set1 isSubsetOfSet:set2];
    NSLog(@"isBool->%d",isBool);    //isBool->0
    // 是否有交集
    isBool = [set1 intersectsSet:set2];
    NSLog(@"isBool->%d",isBool);    //isBool->1
    // 是否相等
    isBool = [set1 isEqualToSet:set2];
    NSLog(@"isBool->%d",isBool);    //isBool->0

3. 集合转数组

    NSSet *set = [NSSet set];
    set = [NSSet setWithArray:@[@"1",@"2",@"3",@"4",@"56789"]];
    NSArray *array = [set allObjects];
    NSLog(@"array->%@",array);//3,1,56789,4,2

4. 获取NSSet元素

    NSSet<NSString *> *set1 = [NSSet setWithObjects:@"12",@"Yes",@"56",@"caodan", nil];
    // 所有成员
    NSArray *array = set1.allObjects;
    NSLog(@"set1->%@", array);  //Yes,caodan,12,56
    // 随机获取
    NSString *anyObject = [set1 anyObject];
    NSLog(@"anyObject->%@", anyObject); //Yes

5. 过滤NSSet元素

    NSSet *set = [NSSet set];
    set = [NSSet setWithArray:@[@"1",@"2",@"3",@"4",@"5"]];
    NSLog(@"set->%@,count->%ld",set,set.count);//set->3,1,4,2,5 ,count->5

    // 1.通过NSPredicate过滤
    NSPredicate *predicate = [NSPredicate predicateWithBlock:^BOOL(id  _Nullable evaluatedObject, NSDictionary<NSString *,id> * _Nullable bindings) {
        if ([evaluatedObject integerValue] >= 3) {
            return NO;
        }
        return YES;
    }];
    set = [set filteredSetUsingPredicate:predicate];
    NSLog(@"set->%@,count->%ld",set,set.count);//set->1,2,count->2

    // 2.用block过滤
    set = [set objectsWithOptions:NSEnumerationConcurrent passingTest:^BOOL(NSString * _Nonnull obj, BOOL * _Nonnull stop) {
        if (obj.integerValue > 3) {
            return NO;
        }
        return YES;
    }];
    NSLog(@"set->%@",set);//set->2,1,3

6. 排序

    // 降序排列
    NSSortDescriptor *sortD = [NSSortDescriptor sortDescriptorWithKey:nil ascending:NO];
    NSArray<NSSortDescriptor *> *sortDs = [NSArray arrayWithObjects:sortD, nil];
    NSArray<NSString *> *array = [set sortedArrayUsingDescriptors:sortDs];
    NSLog(@"%@", array); //56789,4,3,2,1

7. 可变集合创建

    // 快速创建
    NSMutableSet *set1 = [NSMutableSet setWithArray:@[@"1",@"2",@"3",@"4",@"5"]];
    // init方法创建
    NSMutableSet *mSet = [[NSMutableSet alloc] init];
    [mSet addObject:@"9"];

8. 删除集合的元素

    // 在set1中删除set2中相同的元素
    NSMutableSet *set1 = [NSMutableSet setWithArray:@[@"1",@"2",@"3",@"4",@"5"]];
    NSSet *set2 = [NSSet setWithArray:@[@"1",@"2"]];
    [set1 minusSet:set2];
    NSLog(@"set1->%@",set1);//set1->3,4,5

    // 删除指定元素
    NSMutableSet *set1 = [NSMutableSet setWithArray:@[@"1",@"2",@"3",@"4",@"5"]];
    [set1 removeObject:@"3"];
    NSLog(@"set1->%@",set1);//set1->1,4,2,5