Tryable NSDictionary

tryable_dictionary.md

Can I do something like this?

@implementation NSObject (Tryable)

- (id)tryWithKey:(id)key {
    if (!self) return [NSNull null];
    if (![self isKindOfClass:NSDictionary.class]) return [NSNull null];
    if (![(NSDictionary *)self objectForKey:key]
        || [(NSDictionary *)self objectForKey:key] == [NSNull null]) {
        return [NSNull null];
    }
    return ((NSDictionary *)self)[key];
}

@end

Thus, when I handling NSDictionary, I can just ...

id whatIWant = [[[dict tryWithKey:@"aaa"] tryWithKey:@"bbb"] tryWithKey:@"ccc"];