Singleton: Difference between revisions
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({{Omit From|ALGOL 68}} <!-- it isn't immediately obvious that ALGOL 68 is object oriented -->) |
(→{{header|Tcl}}: Tighten, comment) |
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=={{header|Tcl}}== |
=={{header|Tcl}}== |
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{{works with|Tcl|8.6}} |
{{works with|Tcl|8.6}} <br> |
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{{works with|Tcl|8.5}}and the [http://wiki.tcl.tk/TclOO TclOO package] |
{{works with|Tcl|8.5}} and the [http://wiki.tcl.tk/TclOO TclOO package] |
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ref http://wiki.tcl.tk/21595 |
ref http://wiki.tcl.tk/21595 |
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<lang tcl>package require Tcl 8.6 |
<lang tcl>package require Tcl 8.6 |
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# This is a metaclass, a class that defines the behavior of other classes |
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oo::class create singleton { |
oo::class create singleton { |
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superclass oo::class |
superclass oo::class |
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variable object |
variable object |
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unexport create ;# Doesn't make sense to have named singletons |
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method create {name args} { |
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if {![info exists object]} { |
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set object [next $name {*}$args] |
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} |
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return $object |
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} |
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method new args { |
method new args { |
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if {![info exists object]} { |
if {![info exists object]} { |
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} |
} |
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singleton create example { |
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self mixin singleton |
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method counter {} { |
method counter {} { |
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my variable count |
my variable count |
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