if ([[dict allKeys] containsObject:key) {
// contains key
}
if ([dict objectForKey:key]) { //objectForKey will return nil if a key doesn't exists.
// contains key
}
if ([[dict allKeys] containsObject:key) {
// contains key
}
if ([dict objectForKey:key]) { //objectForKey will return nil if a key doesn't exists.
// contains key
}