# This is a simple study for a chan command as # suggested in TIP 208. The following commands # are implemented # # chan blocked ; # fblocked # chan close ; # close # chan fconfigure ; # fconfigure # chan open ; # open # chan puts ; # puts # # We define here a Class chan, which is used # to provide an ensemble-like interface as well # as an object oriented interface (creating instances). # We use here xotcl's forwarding mechanism. The # same could be achieved via renaming or by implementing # the methods in C.
Class chan
chan proc unknown {m args} {
chan puts "unknown chan method '$m $args' called
defined: [lsort [my info commands]]"
}
chan forward blocked ::fblocked
chan forward close ::close
chan forward fconfigure ::fconfigure
chan forward open ::open
chan forward puts ::puts # Now we can use the chan command:
set c [chan open /tmp/junk w] chan puts -nonewline $c "hello" chan puts $c " world" chan close $c chan xxx
# # In order to define an OO interface for # streams, we can extend the definitions:
# allow configuration of a stream name
chan parameter stream
# redefine "new" such it creates and
# opens a stream and creates as well an instance
chan proc new args {
set stream [eval chan open $args]
my create $stream -stream $stream ;# create object
}
# close stream and destroy object
chan instproc destroy {} {
chan close [my stream]
next
}
# handle other subcommands (methods) via unknown
chan instproc unknown {m args} {
set valid [lsort [chan info instcommands]]
stderr puts "unknown chan method '$m' $args called;
defined methods: $valid"
}
# define forwarders to the chan ensemble
chan instforward puts ::chan puts {%@-1 %my stream}
chan instforward blocked ::chan fblocked {%my stream}
chan instforward fconfigure ::chan fconfigure {%my stream}
# create standard streams
chan create stdout -stream stdout
chan create stderr -stream stderr
# Now we can use the chan OO interface
set c [chan new /tmp/junk w] $c puts -nonewline "hello" $c puts -nonewline " world" $c puts "" $c xxx stderr puts "currently open streams: [chan info instances]" $c destroy stderr puts "currently open streams: [chan info instances]"
# A reflection interface an be established # - on the object level (per stream) via a mixin class, or # - on the class level (for all streams) via a instmixin class, # - as well as a mixin on the chan command...
Class StreamReflect foreach m {puts blocked fconfigure} {
StreamReflect instproc $m args {
puts stderr " before [self proc] $args"
set r [next]
puts stderr " after [self proc] returning <$r>"
return $r
}}
puts ===== chan instmixin StreamReflect set c [chan new /tmp/junk w] $c puts "hello" stderr puts "currently open streams: [chan info instances]" $c destroy puts ===== chan mixin StreamReflect set c [chan open /tmp/junk w] chan puts $c "hello" chan close $c puts =====
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Category XOTcl Code