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Function `object.update`

Calls create if key doesn't exist in the associative array, otherwise calls update. create returns a corresponding value for key. update accepts a key parameter. If it returns a value, the value is set for key.


						
				void update(K, V, C, U)
				(
				

				  ref V[K] aa,
				

				  K key,
				

				  scope C create,
				

				  scope U update
				

				)
				

				if (is(typeof(create()) : V) && (is(typeof(update(aa[K.init])) : V) || is(typeof(update(aa[K.init])) == void)));

Parameters

Name	Description
aa	The associative array.
key	The key.
create	The callable to create a value for `key`. Must return V.
update	The callable to call if `key` exists. Takes a K argument, returns a V or void.

Example

int[string] aa;

// create
aa.update("key",
    () => 1,
    (int) {} // not executed
    );
writeln(aa["key"]); // 1

// update value by ref
aa.update("key",
    () => 0, // not executed
    (ref int v) {
        v += 1;
    });
writeln(aa["key"]); // 2

// update from return value
aa.update("key",
    () => 0, // not executed
    (int v) => v * 2
    );
writeln(aa["key"]); // 4

// 'update' without changing value
aa.update("key",
    () => 0, // not executed
    (int) {
        // do something else
    });
writeln(aa["key"]); // 4

Authors

Walter Bright, Sean Kelly

License

Boost License 1.0.