NSMutableArray check if object already exists

iphone objective-c ios nsmutablearray

79,001

Solution 1

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.

Solution 2

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
}

Solution 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];
}

Solution 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;
}

Solution 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.

View more solutions

79,001

Neelesh

iOS dev

Updated on April 13, 2020

Comments

Neelesh about 4 years
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 ?
- knuku almost 13 years
  
  It is a logic mistake, see my answer
Neelesh almost 13 years

@NR4TR: i want to compare the names alone. Not the entire object
Neelesh almost 13 years

First, I want to compare the names alone and not the entire object.
knuku almost 13 years

Consider reading documentation about isEquals method, it could help
Simon Lee almost 13 years

Yes, the idea of overriding the isEquals is that you can then define what you consider 'equal'. Normally the runtime will look at two objects and if they are not the same instance will return false. By overriding the isEquals method you can say 'actually I don't care if the OBJECTS are not the same, in my eyes, these two items are the same if the name matches.'
Neelesh almost 13 years

Yes i get it now. But when i use the code you have updated, I get the following error [Item isEqualToString:]: unrecognized selector sent to instance 0x712ee70
JeremyP almost 13 years

+1 nice answer. Also avoids the mutating collection exception that would happen if the method used in the question actually worked.
knuku almost 13 years

Check your isEqual: method implementation inside your Item class
Neelesh almost 13 years

sorry, I do not seem to follow. Item is a class that i created myself and I do not have an isEqual method at all. Can you please help me in detail ?
knuku almost 13 years

see updates. just paste this isEqual: method to your Item implementation
Neelesh almost 13 years

I tried the above edited solution. First thing, the program crashes without showing any error. Secondly, the Item is added even if it exists in the datasource list
Neelesh almost 13 years

I still get the same error. [Item isEqualToString:]: unrecognized selector sent to instance 0x712ee70
knuku almost 13 years

please read docs carefully and try to do some debugging yourself, it's really hard to do debugging via comments
Neelesh almost 13 years

@simon: thanks for the answer. But still the program crashes :( I am just banging my head now :(
EmptyStack almost 13 years

@Narayanan, Can you tell in which line the program crashes?
Neelesh almost 13 years

I will try debugging :( I thought this should be simple
Neelesh almost 13 years

@simon: It crashes where we create the predicate. [NSComparisonPredicate isEqualToString:]: unrecognized selector sent to instance 0x7154070
EmptyStack almost 13 years

@Narayanan, Remove the single quotes ' from the predicate format and check. I've edited my answer.
Neelesh almost 13 years

@simon: I am sorry. The program crashes. :( :(
EmptyStack almost 13 years

@Narayanan, Alright. Check if the objects in the addList are getting release somewhere or you have some other problem.
Neelesh almost 13 years

No. They are not released anywhere else
Neelesh almost 13 years

@simon: I am not able to figure it out :(
EmptyStack almost 13 years

@Narayanan, Try to print the iNames in the addList and appDelegate.list and check if they are valid.