44 lines
2.2 KiB
XML
44 lines
2.2 KiB
XML
<?xml version="1.0"?>
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<clause number="17.5.1.2" title="Reference parameters">
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<paragraph>A parameter declared with a ref modifier is a reference parameter. Unlike a value parameter, a reference parameter does not create a new storage location. Instead, a reference parameter represents the same storage location as the variable given as the argument in the method invocation. </paragraph>
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<paragraph>When a formal parameter is a reference parameter, the corresponding argument in a method invocation must consist of the keyword ref followed by a <non_terminal where="12.4">variable-reference</non_terminal> (<hyperlink>12.3.3</hyperlink>) of the same type as the formal parameter. A variable must be definitely assigned before it can be passed as a reference parameter. </paragraph>
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<paragraph>Within a method, a reference parameter is always considered definitely assigned. </paragraph>
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<paragraph>
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<example>[Example: The example <code_example><![CDATA[
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using System;
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class Test
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{
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static void Swap(ref int x, ref int y) {
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int temp = x;
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x = y;
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y = temp;
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}
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static void Main() {
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int i = 1, j = 2;
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Swap(ref i, ref j);
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Console.WriteLine("i = {0}, j = {1}", i, j);
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}
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}
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]]></code_example>produces the output <code_example><![CDATA[
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i = 2, j = 1
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]]></code_example></example>
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</paragraph>
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<paragraph>
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<example>For the invocation of Swap in Main, x represents i and y represents j. Thus, the invocation has the effect of swapping the values of i and j. end example]</example>
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</paragraph>
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<paragraph>In a method that takes reference parameters, it is possible for multiple names to represent the same storage location. <example>[Example: In the example <code_example><![CDATA[
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class A
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{
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string s;
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void F(ref string a, ref string b) {
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s = "One";
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a = "Two";
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b = "Three";
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}
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void G() {
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F(ref s, ref s);
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}
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}
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]]></code_example>the invocation of F in G passes a reference to s for both a and b. Thus, for that invocation, the names s, a, and b all refer to the same storage location, and the three assignments all modify the instance field s. end example]</example> </paragraph>
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</clause>
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