Records

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Revision as of 11:47, 15 July 2007 (edit)
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(Added 'Concepts' Category tag.)
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Bryan (Talk | contribs)
(Added how to get a value out of a record.)
 
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<code> <code>
elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8. elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.
 +</code>
 +
 +== Getting the value of a record element ==
 +
 +<code>
 +1> R1 = #recordname{}. % Uses the defaults.
 +#recordname{element1 = "One",element2 = 2,element3 = three}
 +2> io:format("~p~n", [R1#recordname.element1]). % prints "One"
 +"One"
 +ok
</code> </code>
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<code> <code>
-2> R1 = #recordname{}. % Uses the defaults. +3> R2 = #recordname{}. % Uses the defaults.
#recordname{element1 = "One",element2 = 2,element3 = three} #recordname{element1 = "One",element2 = 2,element3 = three}
-3> R2 = R1#recordname{ element1 = "Two" }. % Only modify one part of the record.+4> R3 = R2#recordname{ element1 = "Two" }. % Only modify one part of the record.
#recordname{element1 = "Two",element2 = 2,element3 = three} #recordname{element1 = "Two",element2 = 2,element3 = three}
</code> </code>

Current revision

Contents

[edit] Defining Records

[edit] Without Defaults

Defining a record in code looks like this: 

-record( recordname, { element1, element2, element3 } ).

Defining one in the interpreter looks like this: 

rd(recordname, {element1, element2, element3}).

[edit] With Defaults

Defining a record in code looks like this: 

-record( recordname, { element1 = "One", element2 = 2, element3 = three } ).

Defining one in the interpreter (what I did to create these examples) looks like this: 

rd(recordname, {element1 = "One", element2 = 2, element3  = three }).


[edit] Matching a Record 

elementTwoTimesEight( #recordname{ element2 = T } ) -> T * 8.

[edit] Getting the value of a record element 

1> R1 = #recordname{}.  % Uses the defaults.
#recordname{element1 = "One",element2 = 2,element3 = three}
2> io:format("~p~n", [R1#recordname.element1]). % prints "One"
"One"
ok


[edit] Modifying a Record 

3> R2 = #recordname{}.  % Uses the defaults. 
#recordname{element1 = "One",element2 = 2,element3 = three}
4> R3 = R2#recordname{ element1 = "Two" }.  % Only modify one part of the record.
#recordname{element1 = "Two",element2 = 2,element3 = three}


[edit] More Information

More information at http://erlang.org/doc/getting_started/records_macros.html#5.3.

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