iOS开发---数组去重 2019-05-25

无序的去重

• 利用NSDictionary的AllKeys（AllValues）方法
  可以将NSArray中的元素存入一个字典，然后利用AllKeys或者AllValues取得字典的所有键或值，这些键或值都是去重的

      NSArray *originalArray = @[@1, @2, @3, @1, @3];
      NSMutableDictionary *dict = [NSMutableDictionary dictionary];
      for (NSNumber *n in originalArray) {
          [dict setObject:n forKey:n];
      }
      NSLog(@"dict: %@",[dict allValues]);

• 2.利用NSSet特性, 放入集合自动去重

      NSArray *originalArray = @[@1, @2, @3, @1, @3];
      NSSet *set = [NSSet setWithArray:originalArray];
      NSLog(@"result: %@", [set allObjects]);

注：如果需要排序，可以使用NSSortDescriptor类（参考iOS - 排序: NSSortDescriptor）

有序的去重

• 1.开辟新的内存空间(使用containsObject：方法)
  判断是否存在，若不存在则添加到数组中，得到最终结果的顺序不发生变化

      NSArray *originalArray = @[@1, @2, @3, @1, @3];
      NSMutableArray *resultArray = [NSMutableArray array];
      
      for (NSString *item in originalArray) {
          if (![resultArray containsObject:item]) {
              [resultArray addObject:item];
          }
      }
      NSLog(@"resultArray : %@", resultArray);

• 2.通过valueForKeyPath (@"@distinctUnionOfObjects.self")

      NSArray *originalArray = @[@1, @2, @3, @1, @3];
      NSArray *resultArray = [originalArray valueForKeyPath:@"@distinctUnionOfObjects.self"];
      NSLog(@"result: %@", resultArray);

模型对象的去重

1.通过model类的唯一标识来判断

• 定义一个简单的model类

    // Model.h
    @interface Model : NSObject
    
    @property (nonatomic, copy) NSString *ID;
    @property (nonatomic, copy) NSString *name;
    @end
    
    // Model.m
    @implementation Model
    @end

• 去除数组中重复model对象

    //创建model类对象
    Model *model1 = [[Model alloc]init];
    model1.ID = @"1";
    Model *model2 = [[Model alloc]init];
    model1.ID = @"2";
    Model *model3 = [[Model alloc]init];
    model1.ID = @"3";
    Model *model4 = [[Model alloc]init];
    model1.ID = @"1";
    Model *model5 = [[Model alloc]init];
    model1.ID = @"3";
    //添加到数组中
    NSMutableArray *originalArray = [NSMutableArray arrayWithArray:@[model1,model2,model3,model4,model5]];
    
    NSMutableArray *resultArray = [NSMutableArray arrayWithArray:originalArray];
    //去重
    for (NSInteger x = 0; x < originalArray.count; x++) {
        
        for (NSInteger y = x+1;y < originalArray.count; y++) {
            Model *tempModel = originalArray[x];
            Model *model = originalArray[y];
            if ([tempModel.ID isEqualToString:model.ID]) {
                [resultArray removeObject:model];
            }
        }
    }
    NSLog(@"result: %@", resultArray);