Delegates: Difference between revisions
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Line 749:
d.Delegate <- new Delegate()
assert (d.operation() = "delegate implementation")</lang>
=={{header|Forth}}==
{{works with|Forth}}
Works with any ANS Forth
Needs the FMS-SI (single inheritance) library code located here:
http://soton.mpeforth.com/flag/fms/index.html
<lang forth>include FMS-SI.f
-1 [if] \ add optional introspection facility to FMS
: fm' ( selector-ID link -- xt | 0 ) \ find method, linked-list search
begin @ dup
while 2dup cell+ @ =
if [ 2 cells ] literal + nip @ exit then
repeat 2drop false ;
: has-meth-L ( obj addr -- xt | 0 )
swap >class over @ + fm' ;
: >xt' ( table-offset ^dispatch -- xt | 0 )
2dup @ > if 2drop false exit then
+ @ ;
: has-meth-D ( obj addr -- xt | 0 )
@ swap @ >xt' ;
: (has-meth) ( obj addr sel-type -- xt | 0 )
seltype-L =
if ( obj addr ) has-meth-L
else ( obj addr ) has-meth-D
then ;
: [has-meth] ( obj "messageName" -- xt | 0 ) \ compile time only, can use ex-meth on xt to execute the method
' >body dup postpone literal cell+ @ postpone literal postpone (has-meth) ; immediate
: has-meth ( obj "messageName" -- xt | 0 ) \ interpret time only, can use ex-meth on xt to execute the method
' >body dup cell+ @ (has-meth) ;
[then]
:class delegate
:m thing ." delegate implementation" ;m
;class
delegate slave
:class delegator
ivar del \ object container
:m !: ( n -- ) del ! ;m
:m init: 0 del ! ;m
:m default ." default implementation" ;m
:m operation
del @ 0= if self default exit then
del @ [has-meth] thing
if del @ thing
else self default
then ;m
;class
delegator master
\ First, without a delegate
master operation \ => default implementation
\ then with a delegate that does not implement "thing"
object o
o master !:
master operation \ => default implementation
\ and last with a delegate that implements "thing"
slave master !:
master operation \ => delegate implementation
</lang>
=={{header|Go}}==
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