Objective-C - 如何比较数组并提取差异？
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Objective-C - How to compare arrays and extract the difference?
提问by marione
Possible duplicate: comparing-two-arrays
可能重复：比较两个数组
I have two NSArray and I'd like to create a new Array with objects from the second array but not included in the first array.
我有两个 NSArray，我想用第二个数组中的对象创建一个新数组，但不包含在第一个数组中。
Example:
NSMutableArray *firstArray = [NSMutableArray arrayWithObjects:@"Bill", @"Ben", @"Chris", @"Melissa", nil];
NSMutableArray *secondArray = [NSMutableArray arrayWithObjects:@"Bill", @"Paul", nil];
The resulting array should be:
[@"Paul", nil];
I solved this problem with a double loop comparing objects into the inner one.
我通过将对象与内部对象进行比较的双循环解决了这个问题。
Is there a better solutions ?
有没有更好的解决方案？
回答by Jean Regisser
回答by teabot
If duplicate items are notsignificant in the arrays, you can use the minusSet:operation of NSMutableSet:
如果重复的项目是不是在阵列显著，你可以使用minusSet:的操作 NSMutableSet：
NSMutableArray *firstArray = [NSMutableArray arrayWithObjects:@"Bill", @"Ben", @"Chris", @"Melissa", nil];
NSMutableArray *secondArray = [NSMutableArray arrayWithObjects:@"Bill", @"Paul", nil];
NSSet *firstSet = [NSSet setWithArray:firstArray];
NSMutableSet *secondSet = [NSMutableSet setWithCapacity:[secondArray count]];
[secondSet addObjectsFromArray:secondArray];
[secondSet minusSet:firstSet]; // result is in `secondSet`
回答by Anil Gupta
I want to compare images from two NSArray. One Array, I was getting from Core Database. Second I have constant array objects.
我想比较来自两个 NSArray 的图像。一个数组，我是从核心数据库中获取的。其次，我有常量数组对象。
I want to know that object of second array is present in Core database or not.
我想知道 Core 数据库中是否存在第二个数组的对象。
Here is code which i used.
这是我使用的代码。
// All object from core data and take into array.
NSFetchRequest *fetchRequest = [[NSFetchRequest alloc]initWithEntityName:@"student"];
NSArray *dbresult = [[NSArray alloc]init];
NSError *error;
@try {
dbresult = [context executeFetchRequest:fetchRequest error:&error];
}
@catch (NSException *exception) {
NSString *logerror = [NSString stringWithFormat:@"error in fetching Rooms from coredata = %@",exception.description];
NSLog(logerror)
}
@finally {
}
/*
Get Unused images from list
*/
NSMutableArray *usedImages = [dbresult valueForKey:@"roomImageLocalPath"];
NSMutableSet *fSet = [NSMutableSet setWithArray:usedImages];
NSMutableSet *sSet = [NSMutableSet setWithCapacity:[newImages count]];
[sSet addObjectsFromArray:newImages];
[sSet minusSet:fSet];
NSArray *unusedImages = [secondSet allObjects];
NSLog(@"unusedImages %@",unusedImages);
