How to implement "group by values" in NSMutableArray?

Question

I am using NSMutableArray. I want to fetch the values by date like we do in SQL group by "log_date".

logMuArray (
        {
        "log_currenttime" = "4:30pm";
        "log_date" = "11.12.2011";
        "log_duration" = "1:30";
    },
        {
        "log_currenttime" = "4:33pm";
        "log_date" = "11.12.2011";
        "log_duration" = "2:21";
    },
        {
        "log_currenttime" = "4:40pm";
        "log_date" = "11.12.2011";
        "log_duration" = "5:30";
    },
        {
        "log_currenttime" = "7:30pm";
        "log_date" = "12.12.2011";
        "log_duration" = "1:30";
    },
        {
        "log_currenttime" = "7:33pm";
        "log_date" = "12.12.2011";
        "log_duration" = "2:21";
    },
        {
        "log_currenttime" = "7:40pm";
        "log_date" = "12.12.2011";
        "log_duration" = "5:30";
    },
        {
        "log_currenttime" = "07:16pm";
        "log_date" = "19.12.2011";
        "log_duration" = "0:07";
    },
        {
        "log_currenttime" = "7:31pm";
        "log_date" = "19.12.2011";
        "log_duration" = "0:04";
    },
        {
        "log_currenttime" = "7:33pm";
        "log_date" = "19.12.2011";
        "log_duration" = "0:03";
    },
        {
        "log_currenttime" = "7:33pm";
        "log_date" = "19.12.2011";
        "log_duration" = "0:06";
    },
        {
        "log_currenttime" = "7:35pm";
        "log_date" = "19.12.2011";
        "log_duration" = "0:05";
    }
)

**So, I have just performed....

 NSLog(@"logMuArray %@",[logMuArray valueForKey:@"log_date"]);

But I want to fetch the UNIQUE dates only.** I have thought about NSPredicate or Mutable Set etc...

logMuArray (
    "11.12.2011",
    "11.12.2011",
    "11.12.2011",
    "12.12.2011",
    "12.12.2011",
    "12.12.2011",
    "19.12.2011",
    "19.12.2011",
    "19.12.2011",
    "19.12.2011",
    "19.12.2011"
)

Thanks in advance.....

EDIT:

I have also heared about "@distinctUnionOfObjects"

......

Is it possible to uniquely identify objects based on two or more keys with same logic? — Ajay Gabani
– Ajay Gabani, Commented Jul 8, 2015 at 4:10
Your question is good, better you should ask a question, because code is also required, so please ask your question in stack overflow. Side by side I have not much idea upon this, but I need a time to solve it. Will try to solve it, but need a code for solving it. Better you post your question at stack overflow with code. thanks — Shivbaba's son
– Shivbaba's son, Commented Jul 8, 2015 at 6:54
it might help you Rebuild an NSArray by grouping objects w.r.t any matching keys in each dictionary in that array — umakanta
– umakanta, Commented Jul 20, 2016 at 5:03

jscs · Accepted Answer · 2011-12-20 07:31:26Z

15

Shanti's answer is close. You want to use the Key-Value Coding collection operator @distinctUnionOfObjects. Place the operator immediately preceding the key which you want it to affect, as if it is a part of the key path you are accessing:

[logMuArray valueForKeyPath:@"@distinctUnionOfObjects.log_date"]

Notice the use of valueForKeyPath:, not valueForKey: The former is a method in the Key-Value Coding protocol, and allows accessing arbitrary depth of attributes. The key path is an NSString made up of dot-separated keys. The result of each key lookup is used in turn to access the next key (starting with the original receiver); by default, valueForKey: is simply called at each step.

answered Dec 20, 2011 at 7:31

jscs

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1 Comment

wod Over a year ago

Can i used it with multiple key path such as [log_currenttime,log_date]

Maulik · Accepted Answer · 2011-12-20 06:50:12Z

3

You should use NSSet for UNIQUE items like :

NSSet *filteredData = [NSSet setWithArray:[logMuArray valueForKey:@"log_date"]];

answered Dec 20, 2011 at 6:50

Maulik

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1 Comment

Shivbaba's son Over a year ago

thanks mogs :) But previously Jash Caswell's anser is also nice and prefferable..

Shanti K · Accepted Answer · 2011-12-20 08:35:56Z

3

You can use KVC for this.

[logMuArray valueForKey:@"@distinctUnionOfArrays.log_date"]

edit: Editing this wrt Josh's Response

[logMuArray valueForKeyPath:@"@distinctUnionOfArrays.log_date"]

edited Dec 20, 2011 at 8:35

answered Dec 20, 2011 at 6:49

Shanti K

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1 Comment

Raj Over a year ago

[logMuArray valueForKeyPath:@"@ distinctUnionOfArrays.log_date"], change valueForKey with valueForKeyPath

Nakkeeran · Accepted Answer · 2011-12-20 07:46:23Z

1

Try this logic might help you

-(NSMutableArray *) makeUnique :(NSMutableArray *) array {    
    int i;
    int count = [array count];
    for (i =0; i< count ; i++) {
        NSRange range = NSMakeRange (i+1, count); 
        [array removeObject:[array objectAtIndex:i] inRange:range];
    }
    return array;
}

answered Dec 20, 2011 at 7:46

Nakkeeran

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Comments

Jesse Black · Accepted Answer · 2011-12-20 06:51:52Z

You can incorporate a set

Here is some example code

NSMutableArray * mArray = [NSMutableArray array];
NSDictionary *d1 = [NSDictionary dictionaryWithObjectsAndKeys:@"foo",@"bar",@"bar",@"oooo",nil];
NSDictionary *d2 = [NSDictionary dictionaryWithObjectsAndKeys:@"boo",@"bar",@"bar",@"oooo",nil];
NSDictionary *d3 = [NSDictionary dictionaryWithObjectsAndKeys:@"boo",@"bar",@"bar",@"oooo",nil];
[mArray addObject:d1];
[mArray addObject:d2];
[mArray addObject:d3];
NSLog(@"the array\n%@", mArray);
NSLog(@"just bar %@", [mArray valueForKey:@"bar"]);
//get unique values
NSSet * set = [NSSet setWithArray:[mArray valueForKey:@"bar"]];
NSLog(@"unique just bar %@", [set allObjects]);

and here is the output

2011-12-20 01:50:59.034 TestEnvironment[32401:207] the array
(
        {
        bar = foo;
        oooo = bar;
    },
        {
        bar = boo;
        oooo = bar;
    },
        {
        bar = boo;
        oooo = bar;
    }
)
2011-12-20 01:50:59.036 TestEnvironment[32401:207] just bar (
    foo,
    boo,
    boo
)
2011-12-20 01:50:59.038 TestEnvironment[32401:207] unique just bar (
    foo,
    boo
)

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