Determining if Swift dictionary contains key and obtaining any of its values

I am currently using the following (clumsy) pieces of code for determining if a (non-empty) Swift dictionary contains a given key and for obtaining one (any) value from the same dictionary.

How can one put this more elegantly in Swift?

// excerpt from method that determines if dict contains key
if let _ = dict[key] {
    return true
}
else {
    return false
}

// excerpt from method that obtains first value from dict
for (_, value) in dict {
    return value
}

You don't need any special code to do this, because it is what a dictionary already does. When you fetch dict[key] you know whether the dictionary contains the key, because the Optional that you get back is not nil (and it contains the value).

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
}

Why not simply check for dict.keys.contains(key)? Checking for dict[key] != nil will not work in cases where the value is nil. As with a dictionary [String: String?] for example.

The accepted answer let keyExists = dict[key] != nil will not work if the Dictionary contains the key but has a value of nil.

If you want to be sure the Dictionary does not contain the key at all use this (tested in Swift 4).

if dict.keys.contains(key) {
  // contains key
} else { 
  // does not contain key
}

Looks like you got what you need from @matt, but if you want a quick way to get a value for a key, or just the first value if that key doesn’t exist:

extension Dictionary {
    func keyedOrFirstValue(key: Key) -> Value? {
        // if key not found, replace the nil with 
        // the first element of the values collection
        return self[key] ?? first(self.values)
        // note, this is still an optional (because the
        // dictionary could be empty)
    }
}

let d = ["one":"red", "two":"blue"]

d.keyedOrFirstValue("one")  // {Some "red"}
d.keyedOrFirstValue("two")  // {Some "blue"}
d.keyedOrFirstValue("three")  // {Some "red”}

Note, no guarantees what you'll actually get as the first value, it just happens in this case to return “red”.

My solution for a cache implementation that stores optional NSAttributedString:

public static var attributedMessageTextCache    = [String: NSAttributedString?]()

    if attributedMessageTextCache.index(forKey: "key") != nil
    {
        if let attributedMessageText = TextChatCache.attributedMessageTextCache["key"]
        {
            return attributedMessageText
        }
        return nil
    }

    TextChatCache.attributedMessageTextCache["key"] = .some(.none)
    return nil

If you want to return the value of the key you can use this extension

extension Dictionary {
    func containsKey(_ key: Key) -> Value? {
        if let index = index(forKey: key){
            return self.values[index]
        }
        return nil
    }
}

if dictionayTemp["quantity"] != nil
    {
            
  //write your code
    }

If you are dealing with dictionary that may contain nil value for a key then you can check existence of key by:

dictionay.index(forKey: item.key) != nil

For getting first value in dictionary:

dictionay.first?.value // optional since dictionary might be empty