Better way to compare custom objects of two NSArray and list out distinct objects in those array's

Question

I have a model object called car which has following attributes

Name
Color
Type

In an array(Name: oldArray) I have several car objects. In a common Interval I will hit an API and get an another array (Name: newArray) of several car object. I need to compare two arrays and get the list of unique Items and show it to user.

Conditions. 1. If the object from newArray is not in oldArray then I need to Inform user that he has a new car along with the car name 2. If the object from oldArray is not in newArray then I need to Inform User that he has sold his car along with the car name

I have created the following method

- (NSMutableArray *)getModifiedUserCarsFrom:(NSMutableArray *)savedCars NewCars:(NSMutableArray *)newCars {

    NSMutableArray *loopArray1;
    NSMutableArray *loopArray2;
    NSMutableArray *modifiedCars = [NSMutableArray array];

    if (newCars.count >= savedCars.count) {
        loopArray1 = newCars;
        loopArray2 = savedCars;
    } else {
        loopArray1 = savedCars;
        loopArray2 = newCars;
    }

    for (Car *old in loopArray1) {
        BOOL isCarExist = NO;
        for (Car *new in loopArray2) {
            if ([new.name isEqualToString:old.name]) {
                isCarExist = YES;
                break;
            }
        }
        if (!isCarExist) {
            [modifiedCars addObject:olde];
        }
    }
    return modifiedCars;
}

Is there any better and Faster method than this? Any comments and suggestions are Appreciated.

Generally: implement `isEqual` (which compares all properties) and `hash`, add both arrays to a set and then back to an array and sort. — trojanfoe, May 18 '16 at 09:01
@trojanfoe Thanks For your comments. I tried isEqual but it dint give the desired output. I had same object in both the array's but it return false. — Peer Mohamed Thabib, May 18 '16 at 13:06
@trojanfoe you mean I need to implement both Hash and isEqual to get it work? — Peer Mohamed Thabib, May 18 '16 at 13:11
I believe that is best practise, but I don't think it's required. What I meant was you need to use a set to get your unique set of cars. — trojanfoe, May 18 '16 at 13:12

score 4 · Accepted Answer · answered May 18 '16 at 09:30

//Create NSSet from Array

NSSet* oldset = [NSSet setWithArray:oldArray];
NSSet* newset = [NSSet setWithArray:newArray];

// retrieve the Name of the objects in newset
NSSet* newset_names = [newset valueForKey:@"Name"]; 
// only keep the objects of oldset whose 'Name' are not in newset_names
NSSet* oldset_minus_newset = [oldset filteredSetUsingPredicate:
    [NSPredicate predicateWithFormat:@"NOT Name IN %@",newset_names]];

//And Same can be used for find newset not have name in oldset 

// retrieve the Name of the objects in oldset
NSSet* oldset_names = [oldset valueForKey:@"Name"]; 
// only keep the objects of newset whose 'Name' are not in oldset_names
NSSet* new_minus_oldset = [newset filteredSetUsingPredicate:
    [NSPredicate predicateWithFormat:@"NOT Name IN %@",oldset_names]];

//Now convert back to Array from sets
NSArray *new_minus_oldArray = [new_minus_oldset allObjects];
NSSet* oldset_minus_newArray = [oldset_minus_newset allObjects];

The solution works great and much faster. Thank you so much for your answer — Peer Mohamed Thabib, May 19 '16 at 06:17

score 1 · Answer 2 · answered May 18 '16 at 09:06

1

Use this below code,

its first array(savedCars) same objects in second array(newCars), if you use below code, its automatically remove the same objects in first array(savedCars).

[savedCars removeObjectsInArray: newCars];

hope its helpful

answered May 18 '16 at 09:06

Iyyappan Ravi

3,205
2
16
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its check the two array objects, same objects to be removed then get the remaining objects only – Iyyappan Ravi May 18 '16 at 09:20
@IyyappanRavi Since I am using the array to loop through, if i try to remove it inside loop it won't crash? – Peer Mohamed Thabib May 18 '16 at 13:09

Better way to compare custom objects of two NSArray and list out distinct objects in those array's

2 Answers2