for each loop in Objective-C for accessing NSMutable dictionary

Question

I am finding some difficulty in accessing mutable dictionary keys and values in Objective-C   Suppose I have this   NSMutableDictionary  xyz   NSMutableDictionary alloc  init     I can set keys and values  Now  I just want to access each key and value  but I don t know the number of keys set   In PHP it is very easy  something as follows   foreach   xyz as  key   gt   value    How is it possible in Objective-C

User · Answer

The easiest way to enumerate a dictionary is

for (NSString *key in tDictionary.keyEnumerator) 
{
    //do something here;
}

where tDictionary is the NSDictionary or NSMutableDictionary you want to iterate.

User · Answer

You can use - NSDictionary allKeys  to access all the keys and loop through it

User · Answer

for  NSString  key in xyz        id value   xyz key          do stuff     This works for every class that conforms to the NSFastEnumeration protocol  available on 10 5  and iOS   though NSDictionary is one of the few collections which lets you enumerate keys instead of values  I suggest you read about fast enumeration in the Collections Programming Topic   Oh  I should add however that you should NEVER modify a collection while enumerating through it

User · Answer

I suggest you to read the Enumeration  Traversing a Collection   s Elements part of the Collections Programming Guide for Cocoa  There is a sample code for your need

User · Answer

If you need to mutate the dictionary while enumerating   for  NSString  key in xyz allKeys         xyz setValue  NSNumber numberWithBool YES  forKey key

User · Answer

Just to not leave out the 10 6  option for enumerating keys and values using blocks      dict enumerateKeysAndObjectsUsingBlock   id key  id object  BOOL  stop        NSLog             key  object         If you want the actions to happen concurrently    dict enumerateKeysAndObjectsWithOptions NSEnumerationConcurrent                               usingBlock   id key  id object  BOOL  stop        NSLog             key  object

User · Answer

Fast enumeration was added in 10 5 and in the iPhone OS  and it s significantly faster  not just syntactic sugar  If you have to target the older runtime  i e  10 4 and backwards   you ll have to use the old method of enumerating   NSDictionary  myDict       some keys and values     NSEnumerator  keyEnum    myDict keyEnumerator   id key   while   key    keyEnum nextObject          id value    myDict objectForKey key           do work with  value          You don t release the enumerator object  and you can t reset it  If you want to start over  you have to ask for a new enumerator object from the dictionary

[objective-c] for each loop in Objective-C for accessing NSMutable dictionary

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