Map

Maps are associative containers implemented as pairs each of which maps a key to a value. You can create a map by placing a series of comma-separated entries inside square brackets. Each entry is a key and a value separated by a colon:

    // create a new map with 4 entries
    var d = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];

    // map has a count property
    var n = d.count;    // n is 4

    // create an empty map
    var map = [:];

Looking up values

You can access an element from a list by calling the subscript operator [] on it with the key of the element you want:

    var names = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];
    names["Mark"];      // 1
    names["Andrew"];    // 2

Iterating items

The subscript operator works well for finding values when you know the key you’re looking for, but sometimes you want to see everything that’s in the map. Since the Map class implements the iterator method (through the keys method), you can easily use it in a for loop:

    var people = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];
    for (var name in people.keys()) {
        System.print("Current name is " + name);
    }

Adding items

An item can be added to a map by simply setting a key/value:

    var people = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];
    people["Kiara"] = 5;    // people now contains the "Kiara" key with value 5

Removing items

The remove method has been added to the map class as a conveniente way to remove keys:

    var people = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];
    people.remove("Paul");
    people.remove("Ross");
    return people.count; // 2 is returned in this case

Retrieving keys

The keys method has been added to the map class as a conveniente way to get access to all keys:

    var people = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];
    return people.keys; // ["Mark", "Andrew", "Paul", "Ross"] is returned in this case

Checking for a key

To check if a key has been added to a map you can use the he hasKey method:

    var people = ["Mark":1, "Andrew":2, "Paul":3, "Ross":4];
    return people.hasKey("Max"); // false is returned in this case because the "Max" key is not in the people map