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Author:halw

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Date:2008-10-14T02:27:13.000000Z


git-svn-id: https://svn.eiffel.com/eiffel-org/trunk@80 abb3cda0-5349-4a8f-a601-0c33ac3a8c38
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halw
2008-10-14 02:27:13 +00:00
parent b2f92d3e33
commit 062493b5b9
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documentation/current/method/invitation-eiffel-i2e/i2e-classes.wiki
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@@ -95,7 +95,7 @@ The language definition guarantees automatic initialization, so that the initial
The other public features, <code> withdraw deposit, open, </code> and <code> may_withdraw </code> are straight-forward routines. The special entity <code> Result </code>, used in <code> may_withdraw </code>, denotes the function result; it is initialized on function entry to the default value of the function's result type. You may only use <code> Result </code> in functions.
The secret procedure <code> add </code> serves for the implementation of the public procedures <code> deposit </code> and <code> withdraw </code>; the designer of <code> ACCOUNT </code> judged it too general to be exported by itself. The clause <code> = 1000 </code> introduces <code> minimum_balance </code> as a constant attribute, which will not occupy any space in instances of the class; in contrast, every instance has a field for every non-constant attribute such as <code> balance </code>.
The secret procedure <code> add </code> serves for the implementation of the public procedures <code> deposit </code> and <code> withdraw </code>; the designer of <code> ACCOUNT </code> judged it too general to be exported by itself. The clause "<code> = 1000 </code>" introduces <code> minimum_balance </code> as a constant attribute, which will not occupy any space in instances of the class; in contrast, every instance has a field for every non-constant attribute such as <code> balance </code>.
In Eiffel's object-oriented programming style any operation is relative to a certain object. A client invoking the operation specifies this object by writing the corresponding entity on the left of the dot, as <code> acc </code> in <code> acc.open ("Jill") </code>. Within the class, however, the "current" instance to which operations apply usually remains implicit, so that unqualified feature names, such as <code> owner </code> in procedure <code> open </code> or <code> add </code> in <code> deposit </code>, mean "the <code> owner </code> attribute or <code> add </code> routine relative to the current instance".