20 lines
1.1 KiB
XML
20 lines
1.1 KiB
XML
<?xml version="1.0"?>
|
|
<clause number="17.10.6" title="Optional instance constructor parameters">
|
|
<paragraph>
|
|
<note>[Note: The this(...) form of constructor initializer is commonly used in conjunction with overloading to implement optional instance constructor parameters. In the example <code_example><![CDATA[
|
|
class Text
|
|
{
|
|
public Text(): this(0, 0, null) {}
|
|
public Text(int x, int y): this(x, y, null) {}
|
|
public Text(int x, int y, string s) {
|
|
// Actual constructor implementation
|
|
}
|
|
}
|
|
]]></code_example>the first two instance constructors merely provide the default values for the missing arguments. Both use a this(...) constructor initializer to invoke the third instance constructor, which actually does the work of initializing the new instance. The effect is that of optional constructor parameters: <code_example><![CDATA[
|
|
Text t1 = new Text(); // Same as Text(0, 0, null)
|
|
Text t2 = new Text(5, 10); // Same as Text(5, 10, null)
|
|
Text t3 = new Text(5, 20, "Hello");
|
|
]]></code_example>end note]</note>
|
|
</paragraph>
|
|
</clause>
|