Difference between revisions of "Is"
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{{Is}} | {{Is}} | ||
| − | The [[Reserved word|reserved word]] <syntaxhighlight lang=" | + | The [[Reserved word|reserved word]] <syntaxhighlight lang="delphi" inline>is</syntaxhighlight> appears as: |
| − | |||
| − | |||
| − | + | * an [[Operator|operator symbol]] in [[object-oriented programming]], or as a | |
| + | * a modifier qualifying [[Procedural variable|routine variable]] (<syntaxhighlight lang="delphi" inline>is nested</syntaxhighlight>). | ||
| − | <syntaxhighlight> | + | == Operator == |
| − | + | ||
| − | + | The operator <syntaxhighlight lang="delphi" inline>is</syntaxhighlight> tests, whether an object (first operand) is an instance of a [[Class|class]] or its children. | |
| − | + | <syntaxhighlight lang="delphi">fruit is citrusFruit</syntaxhighlight>is equivalent to<syntaxhighlight lang="delphi">fruit.inheritsFrom(citrusFruit)</syntaxhighlight>. | |
| − | </syntaxhighlight> | + | The [[expression]] is [[false and true|<syntaxhighlight lang="pascal" inline>true</syntaxhighlight>]] if and only if <syntaxhighlight lang="pascal" inline>fruit</syntaxhighlight> descends from <syntaxhighlight lang="pascal" inline>citrusFruit</syntaxhighlight>. |
| + | |||
| + | == Modifier == | ||
| + | |||
| + | If <syntaxhighlight lang="pascal" inline>{$modeSwitch nestedProcVars+}</syntaxhighlight> or [[Mode iso|<syntaxhighlight lang="pascal" inline>{$mode ISO}</syntaxhighlight>]] routine variables declared with the modifier <syntaxhighlight lang="delphi" inline>is nested</syntaxhighlight> allows those to be assigned to nested routines. | ||
| + | Otherwise only global routines' addresses can be assigned to routine variables. | ||
Latest revision as of 09:07, 16 May 2020
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The reserved word is appears as:
- an operator symbol in object-oriented programming, or as a
- a modifier qualifying routine variable (
is nested).
Operator
The operator is tests, whether an object (first operand) is an instance of a class or its children.
fruit is citrusFruit
is equivalent to
fruit.inheritsFrom(citrusFruit)
.
The expression is true if and only if fruit descends from citrusFruit.
Modifier
If {$modeSwitch nestedProcVars+} or {$mode ISO} routine variables declared with the modifier is nested allows those to be assigned to nested routines.
Otherwise only global routines' addresses can be assigned to routine variables.
