CODEWITHSUNDEEP
iphoneobjective-ccocoacocoa-touchnsdictionary
Sheehan Alam
Sheehan Alam

Reputation: 60909

How can I get the first element in an NSDictionary?

I have an array of NSDictionaries. How can I pull out the first element in the dictionary?

   NSArray *messages = [[results objectForKey:@"messages"] valueForKey:@"message"];         
    for (NSDictionary *message in messages)
    {
        STObject *mySTObject = [[STObject alloc] init];
        mySTObject.stID = [message valueForKey:@"id"];      
        stID = mySTObject.stID;
    }

Upvotes: 39

Views: 53986

Answers (8)

Wevah
Wevah

Reputation: 28242

[Updated to use firstObject, as described in another answer, which has the benefit of returning nil for an empty array.]

There is no "first" element in an NSDictionary; its members have no guaranteed order. If you just want one object from a dictionary, but don't care which key it's associated with, you can do:

id val = yourDict.allValues.firstObject;

(There's also lastObject, which has been around since 10.0(!).)

(Old, pre 10.6 version:)

id val = nil;
NSArray *values = [yourDict allValues];
    
if ([values count] != 0)
    val = [values objectAtIndex:0];

Upvotes: 63

Ivan Rovelov
Ivan Rovelov

Reputation: 651

Simplest:

[[dict objectEnumerator] nextObject];

Upvotes: 3

ASLLOP
ASLLOP

Reputation: 161

NSArray has a selector named firstObject that simplifies the code and makes it more readable:

id val = [[yourDict allValues] firstObject];

If yourDict is empty val will be nil, so is not necessary to check the dictionary/array size.

Upvotes: 7

1218GG
1218GG

Reputation: 393

If someone is still looking for answer for this type of situation then can refer this:

// dict is NSDictionary

// [dict allKeys] will give all the keys in dict present

// [[dict allKeys]objectAtIndex:0] will give from all the keys object at index 0 because [dict allKeys] returns an array.

[[dict allKeys]objectAtIndex:0];

Upvotes: 2

LZM
LZM

Reputation: 189

According to Apple, calls to allKeys or allValues incur the cost of creating new arrays:

A new array containing the dictionary’s values, or an empty array if the dictionary has no entries (read-only)

So, an alternative option that does not incur such cost could look like this:

NSString* key = nil;
for(key in yourDict)
{ // this loop will not execute if the dictionary is empty
   break; // exit loop as soon as we enter it (key will be set to some key)
}
id object = yourDict[key]; // get object associated with key. nil if key doesn't exist.

Note: If the dictionary is empty, the key will remain nil, and the object returned will also be nil, we therefore don't need special handling of the case where the dictionary is actually empty.

Upvotes: 2

Tea
Tea

Reputation: 306

Try this:

NSDictionary *firstValue = [responseObject objectAtIndex:0];

Upvotes: -2

n0_quarter
n0_quarter

Reputation: 538

If you have NSDictionary named message, It's pretty simple: 

message[[[message allKeys] objectAtIndex:0]];

But you have to be sure (or better check) that your dictionary has at least one element. Here is how you can check it:

if ([message allKeys] > 0) NSLog(@"%@", message[[[message allKeys] objectAtIndex:0]]);

But NSDictionary has no guaranteed order, so you probably should use this code only if your dictionary has only one element.

[UPDATE] It's also good idea to use this if you need to get ANY element of dictionary

Upvotes: 0

Martin Cote
Martin Cote

Reputation: 29882

NSDictionaries are unordered, meaning that there are not first or last element. In fact, the order of the keys are never guaranteed to be the same, even in the lifetime of a specific dictionary.

If you want any object, you can get one of the keys:

id key = [[message allKeys] objectAtIndex:0]; // Assumes 'message' is not empty
id object = [message objectForKey:key];

Upvotes: 25

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