NSMutableArray check if object already exists

问题

I am not sure how to go about this. I have an NSMutableArray (addList) which holds all the items to be added to my datasource NSMutableArray.

I now want to check if the object to be added from the addList array already exists in the datasource array. If it does not exist add the item, if exists ignore.

Both the objects have a string variable called iName which i want to compare.

Here is my code snippet

-(void)doneClicked{
    for (Item *item in addList){
        /*
        Here i want to loop through the datasource array 
        */
        for(Item *existingItem in appDelegate.list){
            if([existingItem.iName isEqualToString:item.iName]){
                // Do not add
            }
            else{
                [appDelegate insertItem:item];
            } 
        }
}

But i find the item to be added even if it exists.

What am i doing wrong ?

回答1:

There is a very useful method for this in NSArray i.e. containsObject.

NSArray *array;
array = [NSArray arrayWithObjects: @"Nicola", @"Margherita",                                       @"Luciano", @"Silvia", nil];
if ([array containsObject: @"Nicola"]) // YES
{
    // Do something
}

回答2:

I found a solution, may not be the most efficient of all, but atleast works

NSMutableArray *add=[[NSMutableArray alloc]init];

for (Item *item in addList){
        if ([appDelegate.list containsObject:item])
            {}
        else
            [add addObject:item];
}

Then I iterate over the add array and insert items.

回答3:

Use NSPredicate.

NSArray *list = [[appDelegate.list copy] autorelease];

for (Item *item in addList) {

    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"iName MATCHES %@", item.iName];
    NSArray *filteredArray = [list filteredArrayUsingPredicate:predicate];
    if ([filteredArray count] > 0) [appDelegate insertItem:item];
}

回答4:

Did you try indexOfObject:?

-(void)doneClicked{
    for (Item *item in addList){
        if([appDelegate.list indexOfObject:item] == NSNotFound){
            [appDelegate insertItem:item];
        }
}

UPDATE: You have a logical mistake, not mistake in code. assume the first array is ['a', 'b', 'c'], and the second is ['a', 'x', 'y', 'z']. When you iterate with 'a' through the second array it won't add 'a' to second array in the first iteration (compare 'a' with 'a') but will add during the second (compare 'a' with 'x'). That is why you should implement isEqual: method (see below) in your 'Item' object and use the code above.

- (BOOL)isEqual:(id)anObject {
    if ([anObject isKindOfClass:[Item class]])
        return ([self.iName isEqualToString:((Item *)anObject).iName]);
    else
        return NO;
}

回答5:

Have a look at NSSet. You can add objects and the object will only be added if the object is unique. You can create a NSSet from an NSArray or vise versa.

回答6:

You can override isEquals and hash on the object so that it returns a YES / NO based on the comparison of the iName property.

Once you have that you can use...

- (void)removeObjectsInArray:(NSArray *)otherArray

To clean the list before adding all the remaining objects.

回答7:

NR4TR said correctly but i think one break statement is sufficient


if([existingItem.iName isEqualToString:item.iName]){
                // Do not add
break;
            }

回答8:

Convert Lowercase and Trim whitespace and then check..

[string lowercaseString];

and

NSString *trim = [string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceCharacterSet]];

回答9:

You compare the addList's first object and appDelegate.list's first object, if they are not equal, you insert the addList's object. The logic is wrong, you should compare one addList's object with every appDelegate.list's object.

来源：https://stackoverflow.com/questions/6291412/nsmutablearray-check-if-object-already-exists

标签

iphone

objective-c

ios

nsmutablearray