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[mcs.git] / docs / ecma334 / 17.4.xml

<?xml version="1.0"?>
<clause number="17.4" title="Fields">
  <paragraph>A field is a member that represents a variable associated with an object or class. A <non_terminal where="17.4">field-declaration</non_terminal> introduces one or more fields of a given type. <grammar_production><name><non_terminal where="17.4">field-declaration</non_terminal></name> : <rhs><non_terminal where="24.2">attributes</non_terminal><opt/><non_terminal where="17.4">field-modifiers</non_terminal><opt/><non_terminal where="11">type</non_terminal><non_terminal where="17.4">variable-declarators</non_terminal><terminal>;</terminal></rhs></grammar_production><grammar_production><name><non_terminal where="17.4">field-modifier</non_terminal>s</name> : <rhs><non_terminal where="17.4">field-modifier</non_terminal></rhs><rhs><non_terminal where="17.4">field-modifiers</non_terminal><non_terminal where="17.4">field-modifier</non_terminal></rhs></grammar_production><grammar_production><name><non_terminal where="17.4">field-modifier</non_terminal></name> : <rhs><keyword>new</keyword></rhs><rhs><keyword>public</keyword></rhs><rhs><keyword>protected</keyword></rhs><rhs><keyword>internal</keyword></rhs><rhs><keyword>private</keyword></rhs><rhs><keyword>static</keyword></rhs><rhs><keyword>readonly</keyword></rhs><rhs><keyword>volatile</keyword></rhs></grammar_production><grammar_production><name><non_terminal where="17.4">variable-declarator</non_terminal>s</name> : <rhs><non_terminal where="17.4">variable-declarator</non_terminal></rhs><rhs><non_terminal where="17.4">variable-declarators</non_terminal><terminal>,</terminal><non_terminal where="17.4">variable-declarator</non_terminal></rhs></grammar_production><grammar_production><name><non_terminal where="17.4">variable-declarator</non_terminal></name> : <rhs><non_terminal where="9.4.2">identifier</non_terminal></rhs><rhs><non_terminal where="9.4.2">identifier</non_terminal><terminal>=</terminal><non_terminal where="19.6">variable-initializer</non_terminal></rhs></grammar_production><grammar_production><name><non_terminal where="19.6">variable-initializer</non_terminal></name> : <rhs><non_terminal where="14.14">expression</non_terminal></rhs><rhs><non_terminal where="19.6">array-initializer</non_terminal></rhs></grammar_production></paragraph>
  <paragraph>A <non_terminal where="17.4">field-declaration</non_terminal> may include a set of attributes (<hyperlink>24</hyperlink>), a new modifier (<hyperlink>17.2.2</hyperlink>), a valid combination of the four access modifiers (<hyperlink>17.2.3</hyperlink>), and a static modifier (<hyperlink>17.4.1</hyperlink>). In addition, a <non_terminal where="17.4">field-declaration</non_terminal> may include a readonly modifier (<hyperlink>17.4.2</hyperlink>) or a volatile modifier (<hyperlink>17.4.3</hyperlink>), but not both The attributes and modifiers apply to all of the members declared by the <non_terminal where="17.4">field-declaration</non_terminal>. It is an error for the same modifier to appear multiple times in a field declaration. </paragraph>
  <paragraph>The type of a <non_terminal where="17.4">field-declaration</non_terminal> specifies the type of the members introduced by the declaration. The type is followed by a list of <non_terminal where="17.4">variable-declarator</non_terminal>s, each of which introduces a new member. A <non_terminal where="17.4">variable-declarator</non_terminal> consists of an identifier that names that member, optionally followed by an &quot;=&quot; token and a  <non_terminal where="19.6">variable-initializer</non_terminal> (<hyperlink>17.4.5</hyperlink>) that gives the initial value of that member. </paragraph>
  <paragraph>The type of a field must be at least as accessible as the field itself (<hyperlink>10.5.4</hyperlink>). </paragraph>
  <paragraph>The value of a field is obtained in an expression using a <non_terminal where="14.5.2">simple-name</non_terminal> (<hyperlink>14.5.2</hyperlink>) or a <non_terminal where="14.5.4">member-access</non_terminal> (<hyperlink>14.5.4</hyperlink>). The value of a non-readonly field is modified using an assignment (<hyperlink>14.13</hyperlink>). The value of a  non-readonly field can be both obtained and modified using postfix increment and decrement operators (<hyperlink>14.5.9</hyperlink>) and prefix increment and decrement operators (<hyperlink>14.6.5</hyperlink>). </paragraph>
  <paragraph>A field declaration that declares multiple fields is equivalent to multiple declarations of single fields with the same attributes, modifiers, and type. <example>[Example: For example <code_example><![CDATA[
class A  
{  
   public static int X = 1, Y, Z = 100;  
}  
]]></code_example>is equivalent to <code_example><![CDATA[
class A  
{  
   public static int X = 1;  
   public static int Y;  
   public static int Z = 100;  
}  
]]></code_example>end example]</example> </paragraph>
</clause>