限制NSArray中的重复条目 [英] Restrict Duplicate entry in NSArray

问题描述

我有一个数组，其中包含一些重复的条目。

I have an array, which contains some duplicate entries.

首先，有没有办法在插入数据时限制重复的条目？

Firstly, is there any way to restrict duplicate entries when data getting inserted?

其次，如果一个数组已经有重复值而不是其他方式，我们只能从该数组中检索唯一值，我听说过关于此的NSSet，但我不知道如何使用它。

Secondly, if an array already having duplicate values than in some other way, we can retrieve only unique values from that array, I heard about NSSet about this, but I have no idea how to use it.

推荐答案

不要使用NSSet 。

您只能在创建时插入元素，并且不能更改创建后包含的元素。

You can only insert elements upon creation and cannot change the elements contained after you have created it.

如果您想动态添加和删除对象，可以使用 NSMutableSet 。

If you want to add and remove objects on the fly, you can use an NSMutableSet.

以下是如何使用 NSSet 和 NSMutableSet ，然后将 NSSet 转换回 NSArray的演示（如果你想这样做）：

Here is a demo of how to use it both NSSet and NSMutableSet, then converting the NSSet back to an NSArray (incase you want to do that):

- (void) NSMutableSetPrintTest
{
    NSMutableSet *mutableSet = [[NSMutableSet alloc] init];

    NSLog(@"Adding 5 objects (3 are duplicates) to NSMutableSet");
    NSString *firstString = @"Hello World";
    [mutableSet addObject:firstString];
    [mutableSet addObject:@"Hello World"];
    [mutableSet addObject:@"Goodbye World"];
    [mutableSet addObject:@"Goodbye World"];
    [mutableSet addObject:@"Goodbye World"];

    NSLog(@"NSMutableSet now contains %d objects:", [mutableSet count]);
    int j = 0;
    for (NSString *string in mutableSet) {
        NSLog(@"%d: %@ <%p>", j, string, string);
        j++;
    }

    NSLog(@"Now, if we are done adding and removing things (and only want to check what is in the Set) we should convert to an NSSet for increased performance.");
    NSSet *immutableSet = [NSSet setWithSet:mutableSet];

    NSLog(@"NSSet now contains %d objects:", [immutableSet count]);
    int i = 0;
    for (NSString *string in immutableSet) {
        NSLog(@"%d: %@ <%p>", i, string, string);
        i++;
    }

    [mutableSet release]; mutableSet = nil;

    NSLog(@"Now, if we are done with the sets, we can convert them back to an NSArray:");
    NSArray *array = [immutableSet allObjects];

    NSLog(@"NSArray contains %d objects", [array count]);
    int k = 0;
    for (NSString *string in array) {
        NSLog(@"%d: %@ <%p>", k, string, string);
        k++;
    }
}

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