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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
Copyright © 1999-2024 by the D Language Foundation | Page generated by ddox.