How to check if an NSDictionary or NSMutableDictionary contains a key?

if ([MyDictionary objectForKey:MyKey]) {
// "Key Exist"
}

Using Swift, it would be:

if myDic[KEY] != nil {
// key exists
}

Yes. This kind of errors are very common and lead to app crash. So I use to add NSDictionary in each project as below:

//.h file code :



@interface NSDictionary (AppDictionary)

- (id)objectForKeyNotNull : (id)key;

@end



//.m file code is as below

#import "NSDictionary+WKDictionary.h"

@implementation NSDictionary (WKDictionary)

- (id)objectForKeyNotNull:(id)key {

id object = [self objectForKey:key];
if (object == [NSNull null])
return nil;

return object;
}

@end

In code you can use as below:

NSStrting *testString = [dict objectForKeyNotNull:@"blah"];

As Adirael suggested `objectForKey` to check key existance but When you call `objectForKey`in nullable dictionary, app gets crashed so I fixed this from following way.

- (instancetype)initWithDictionary:(NSDictionary*)dictionary {
id object = dictionary;

if (dictionary && (object != [NSNull null])) {
self.name = [dictionary objectForKey:@"name"];
self.age = [dictionary objectForKey:@"age"];
}
return self;
}

**Solution for swift 4.2**

So, if you just want to answer the question whether the dictionary contains the key, ask:

let keyExists = dict[key] != nil



If you want the value and you know the dictionary contains the key, say:

let val = dict[key]!

But if, as usually happens, you don't know it contains the key - you want to fetch it and use it, but only if it exists - then use something like `if let`:

if let val = dict[key] {
// now val is not nil and the Optional has been unwrapped, so use it
}

if ( [dictionary[@"data"][@"action"] isKindOfClass:NSNull.class ] ){
//do something if doesn't exist
}

This is for nested dictionary structure

<strike>

if ([[dictionary allKeys] containsObject:key]) {
// contains key
/* Don't use this solution. Look for more details in comments. */
}

</strike>

or

if ([dictionary objectForKey:key]) {
// contains object
}