Add values in NSMutableDictionary in iOS with Objective-C - ios

Question

I'm starting objective-c development and I would like to ask the best way to implement a list of keys and values.
In Delphi there is the class TDictionary and I use it like this:
myDictionary : TDictionary<string, Integer>;
bool found = myDictionary.TryGetValue(myWord, currentValue);
if (found)
{
myDictionary.AddOrSetValue(myWord, currentValue+1);
}
else
{
myDictionary.Add(myWord,1);
}
How can I do it in objective-c? Is there equivalent functions to the above mentioned AddOrSetValue() or TryGetValue()?
Thank you.

Answer 1

You'd want to implement your example along these lines:
EDIT:
//NSMutableDictionary myDictionary = [[NSMutableDictionary alloc] init];
NSMutableDictionary *myDictionary = [[NSMutableDictionary alloc] init];
NSNumber *value = [myDictionary objectForKey:myWord];
if (value)
{
NSNumber *nextValue = [NSNumber numberWithInt:[value intValue] + 1];
[myDictionary setObject:nextValue forKey:myWord];
}
else
{
[myDictionary setObject:[NSNumber numberWithInt:1] forKey:myWord]
}
(Note: you can't store ints or other primitives directly in a NSMutableDictionary, hence the need to wrap them in an NSNumber object, and make sure you call [myDictionary release] when you've finished with the dictionary).

Answer 2

The other answers are correct, but there is more modern syntax for this now. Rather than:
[myDictionary setObject:nextValue forKey:myWord];
You can simply say:
myDictionary[myWord] = nextValue;
Similarly, to get a value, you can use myDictionary[key] to get the value (or nil).

Answer 3

Yep:
- (id)objectForKey:(id)key;
- (void)setObject:(id)object forKey:(id)key;
setObject:forKey: overwrites any existing object with the same key; objectForKey: returns nil if the object doesn't exist.
Edit:
Example:
- (void)doStuff {
NSMutableDictionary *dict = [NSMutableDictionary dictionary];
[dict setObject:#"Foo" forKey:#"Key_1"]; // adds #"Foo"
[dict setObject:#"Bar" forKey:#"Key_2"]; // adds #"Bar"
[dict setObject:#"Qux" forKey:#"Key_2"]; // overwrites #"Bar"!
NSString *aString = [dict objectForKey:#"Key_1"]; // #"Foo"
NSString *anotherString = [dict objectForKey:#"Key_2"]; // #"Qux"
NSString *yas = [dict objectForKey:#"Key_3"]; // nil
}
Reedit: For the specific example there exists a more compact approach:
[dict
setObject:
[NSNumber numberWithInteger:([[dict objectForKey:#"key"] integerValue] + 1)]
forKey:
#"key"
];
Crazy indentation for readability.