Dictionary¶

Init¶

Different types to initialize

let dict = [String: Int]()

let dict2: [String: Int] = [
        "Kautilya": 0,
        "Zeus": 1,
        "Sensehack": 2,
]

let dict3: [String: Int]?

var initProtocol = [String : Int]()
someProtocol["one"] = 1
someProtocol["two"] = 2

let someProtocol = [
    "one" : 1,
    "two" : 2
]

Access¶

Traversing

for (key, value) in dictionaryName {
        // Depending on types you would parse or type cast these data types while printing or utilizing.
    print("Key: \(key) & value: \(value)")
}

Complexity¶

Search: Searching time is always constant in Dictionary as they are hashed internally, so the key is accepted in any common hashable data type and Swift compiler internally generates a Hash value for it. So it’s easy to get those details.

Quirks: Thats the reason that Dictionary aren’t organized in a sorted manner.

Update: It’s also in constant Big O(1) time.

Applications¶

• Great for generating a hash map or keeping track of things in computer science.
• Different data types can be utilized.
• Great for real life enterprise scenarios where restful APIs returns a mix of primitive types in JSON data format.

HashMap¶

func hashTable()  {
        let numbers = [1,4,5,3,3,12,3,5,3,3,6,7,1,2]
        var hashMap = [Int: Int]()

        for number in numbers {
            if (hashMap[number] != nil) {
                hashMap[number]! += 1
            } else {
                hashMap[number] = 1
            }
        }

//        hashMap


        for (keys, values) in hashMap {
            print("\(keys): \(values)")
        }
    }

References¶

SO

Tutorials Point