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NAME

perlboot - åå¦èçé¢åå¯¹è±¡æç¨

DESCRIPTION æè¿°

æä»¥, è®©æä»¬èµ°å¦ä¸æ¡è·¯,åå®ä½ æ²¡æä»»ä½å³äºå¯¹è±¡çæ¦å¿µ. ä½ éè¦äºè§£åç¨åº (perlsub), å¼ç¨ (perlref et. seq.), å å(ææ¨¡å) (perlmod), å¦æè¿ä¸æ¸æ¥çè¯,åæä»ä»¬ææ¸æ¥.

If we could talk to the animals...å¦ææä»¬è½åå¨ç©äº¤è°

è®©æä»¬è®©å¨ç©è®²ä¼å¿è¯:

sub Cow::speak {
print "a Cow goes moooo!\n";
}
sub Horse::speak {
print "a Horse goes neigh!\n";
}
sub Sheep::speak {
print "a Sheep goes baaaah!\n"
}

Cow::speak;
Horse::speak;
Sheep::speak;

ç»ææ¯:

a Cow goes moooo!
a Horse goes neigh!
a Sheep goes baaaah!

# Cow::speak, Horse::speak, Sheep::speak ä¸ä¸å
@pasture = qw(Cow Cow Horse Sheep Sheep);
foreach $animal (@pasture) {
&{$animal."::speak"};
}

ç»ææ¯:

a Cow goes moooo!
a Cow goes moooo!
a Horse goes neigh!
a Sheep goes baaaah!
a Sheep goes baaaah!

ççæ¯è¿æ ·å?

Introducing the method invocation arrow è°ç¨æ¹æ³æ¶çç®å¤´ç¬¦å·

ç°å¨,æä»¬è¯´ "Class->method" æ¯è°ç¨äºå(ææ¨¡å)"Class"ä¸ç "method" æ¹æ³ã(Here, "Class" is used in its "category" meaning, not its "scholastic" meaning.) ä¸æ¯å¾åç¡®,ä¸è¿æä»¬ä¼ä¸æ¥ä¸æ¥çæ¥å. ç°å¨,å¯ä»¥è¿æ ·å:

# Cow::speak, Horse::speak, Sheep::speak as before
Cow->speak;
Horse->speak;
Sheep->speak;

è¾åºä¸º:

a Cow goes moooo!
a Horse goes neigh!
a Sheep goes baaaah!

$a = "Cow";
$a->speak; # invokes Cow->speak

Invoking a barnyard åå»ºä¸ä¸ªç²å£æ£

ç°å¨è®©æä»¬æç®å¤´ç¨å°ç²å£æ£çä¾åä¸ï¼èä¾:

sub Cow::speak {
print "a Cow goes moooo!\n";
}
sub Horse::speak {
print "a Horse goes neigh!\n";
}
sub Sheep::speak {
print "a Sheep goes baaaah!\n"
}

@pasture = qw(Cow Cow Horse Sheep Sheep);
foreach $animal (@pasture) {
$animal->speak;
}

The extra parameter of method invocation æ¹æ³è°ç¨æ¶çé¢å¤åæ°

è¯å¥:

Class->method(@args)

è¿æ ·è°ç¨å½æ° "Class::method"ï¼

Class::method("Class", @args);

sub Sheep::speak {
my $class = shift;
print "a $class goes baaaah!\n";
}

å¦å¤çå¨ç©ä¸æ¤ç±»ä¼¼:

sub Cow::speak {
my $class = shift;
print "a $class goes moooo!\n";
}
sub Horse::speak {
my $class = shift;
print "a $class goes neigh!\n";
}

Calling a second method to simplify things è°ç¨å¦ä¸ä¸ªæ¹æ³ä»¥ç®åæä½

æä»¬å¨ "speak" ä¸è°ç¨ "sound". è¿ä¸ªæ¹æ³æä¾å£°é³çåå®¹.

{ package Cow;
sub sound { "moooo" }
sub speak {
my $class = shift;
print "a $class goes ", $class->sound, "!\n"
}
}

ç°å¨, å½æä»¬è°ç¨ "Cow->speak" æ¶, æä»¬å¨ "speak" ä¸å¾å° "Cow" çç±» $class. ä»ä¼éæ© "Cow->sound" æ¹æ³, ç¶åè¿å "moooo". é£å¦ææ¯ "Horse" å¢?

{ package Horse;
sub sound { "neigh" }
sub speak {
my $class = shift;
print "a $class goes ", $class->sound, "!\n"
}
}

ä»ä»åååå£°é³æåå. å æ¤æä»¬å¯ä»¥å¨CowåHorseä¸å±ç¨ "speak" å? æ¯ç,éè¿ç»§æ¿å®ç°!

Inheriting the windpipes ç»§æ¿æ°ç®¡

{ package Animal;
sub speak {
my $class = shift;
print "a $class goes ", $class->sound, "!\n"
}
}

{ package Cow;
@ISA = qw(Animal);
sub sound { "moooo" }
}

æ³¨æå¢å çæ°ç» @ISA . æä»¬é©¬ä¸è®²å°å®.

ç°å¨å½æä»¬è°ç¨ "Cow->speak" æ¶ä¼åçä»ä¹?

é¦å, Perlæé åæ°åè¡¨. å¨è¿ç§æåµä¸, åªæ "Cow". ç¶åPerl æ¥æ¾ "Cow::speak". ä½æ¯æ¾ä¸å°, æä»¥Perlæ£æ¥ç»§æ¿æ°ç» @Cow::ISA. æ¾å°äº, é£éåªæä¸ä¸ª "Animal"

Perl ç¶åå¨ "Animal" ä¸æ¥æ¾ "speak", "Animal::speak". æ¾å°äº, ç¶åè°ç¨è¯¥åç¨åº, åæ°å¨ä¸å¼å§å°±è¢«åºå®äº.

å¨åç¨åº "Animal::speak" ä¸, $class æ¯ "Cow" (ç¬¬ä¸ä¸ªåæ°). å¨æä»¬è°ç¨ "$class->sound" æ¶, é¦åå¯»æ¾ "Cow->sound" , æ¾å°äº, å æ¤ä¸ç¨æ¥ç @ISA. æå!

å³äº@ISAåºè¯¥æ³¨æçå ç¹é®é¢

ç¥å¥ç @ISA åé (è¯»ä½ "is a" èä¸æ¯ "ice-uh"), å£°æäº "Cow" æ¯ä¸ä¸ª("is a") "Animal"ã æ³¨æå®æ¯ä¸ä¸ªæ°ç»,èä¸æ¯ä¸ä¸ªåå¼, å ä¸ºå¨ä¸ªå«æåµä¸, éè¦å¨å ä¸ªç¶ç±»ä¸å¯»æ¾æ¹æ³.

æç®åçåæ³æ¯å ä¸åå:

@Cow::ISA = qw(Animal);

æèä½¿ç¨åå£°æ:

package Cow;
use vars qw(@ISA);
@ISA = qw(Animal);

å¦æä½ å¸ææåæ¾å°ç¨åºå, å¯ä»¥æ:

package Cow;
use Animal;
use vars qw(@ISA);
@ISA = qw(Animal);

ç®åä¸º:

package Cow;
use base qw(Animal);

è¿å°±ç²¾ç®å¤äº.

Overriding the methods æ¹æ³éè½½

è®©æä»¬æ·»ä¸ä¸åªèé¼ , å®çå£°é³å·®ä¸å¤å¬ä¸å°:

# Animal package from before
{ package Mouse;
@ISA = qw(Animal);
sub sound { "squeak" }
sub speak {
my $class = shift;
print "a $class goes ", $class->sound, "!\n";
print "[but you can barely hear it!]\n";
}
}

Mouse->speak;

è¾åºä¸º:

a Mouse goes squeak!
[but you can barely hear it!]

å¨è¿é, "Mouse" æå®èªå·±çspeak å½æ°, æä»¥ "Mouse->speak" ä¸ä¼è°ç¨"Animal->speak". è¿å«åéè½½ "overriding". å®éä¸, æä»¬çè³ä¸ç¨è¯´"Mouse" æ¯ "Animal", å ä¸º "speak" æç¨å°çæææ¹æ³å¨ "Mouse" ä¸é½æå®ä¹.

é¦å,æä»¬å¯ä»¥ç´æ¥è°ç¨ "Animal::speak" æ¹æ³:

# Animal package from before
{ package Mouse;
@ISA = qw(Animal);
sub sound { "squeak" }
sub speak {
my $class = shift;
Animal::speak($class);
print "[but you can barely hear it!]\n";
}
}

æ³¨ææä»¬å¿é¡»ä½¿ç¨ $class (å ä¹è¯å®æ¯"Mouse") ä½ä¸º "Animal::speak" çç¬¬ä¸ä¸ªåæ°, å ä¸ºæä»¬æ²¡æç¨ç®å¤´ç¬¦å·. é£ä¸ºä»ä¹ä¸ç¨å¢? å¯, å¦ææä»¬å¨é£å¿è°ç¨ "Animal->speak", åç¬¬ä¸ä¸ªåæ°æ¯ "Animal" èä¸æ¯ "Mouse" , è¿æ ·å½è°ç¨ "sound" æ¶, å°±æ¾ä¸å°æ£ç¡®çå½æ°äº.

Starting the search from a different place ä»å¶å®å°æ¹å¼å§å¯»æ¾

# same Animal as before
{ package Mouse;
# same @ISA, &sound as before
sub speak {
my $class = shift;
$class->Animal::speak;
print "[but you can barely hear it!]\n";
}
}

è¿å°±å¯¹äº. ä½¿ç¨è¿ä¸è¯æ³, æä»¬ä» "Animal" å¯»æ¾ "speak", å¨æ¾ä¸å°æ¶å¯»æ¾ "Animal" çç»§æ¿é¾.ä¸ç¬¬ä¸ä¸ªåæ°æ¯ $class, æä»¥ "speak" å"Mouse::sound" é½ä¼è¢«æ£ç¡®å°è°ç¨.

The SUPER way of doing things ä½¿ç¨SUPERæ¹æ³

éè¿æ "Animal" æ¹æ "SUPER" ç±», ç¨åºå¯ä»¥èªå¨å¨ææç¶ç±»ä¸(@ISA):

# same Animal as before
{ package Mouse;
# same @ISA, &sound as before
sub speak {
my $class = shift;
$class->SUPER::speak;
print "[but you can barely hear it!]\n";
}
}

"SUPER::speak" æå³çå¨å½ååç @ISA ä¸å¯»æ¾ "speak", è°ç¨ç¬¬ä¸ä¸ªæ¾å°çå½æ°ãæ³¨æå®ä¸ä¼æ¥æ¾ $class ç @ISA

Where we’re at so far...å°ç°å¨ä¸ºæ¢æä»¬å¦äºäºä»ä¹

æä»¬å·²ç»çå°äºç®å¤´ç¬¦å·è¯æ³:

Class->method(@args);

åå®ççä»·å½¢å¼:

$a = "Class";
$a->method(@args);

å®ä»¬æé è¿æ ·ä¸ä¸ªåæ°åè¡¨:

("Class", @args)

å¹¶è°ç¨

Class::method("Class", @Args);

ä½æ¯ï¼å¦ææ¾ä¸å° "Class::method", ç¨åºä¼æ¥ç @Class::ISA (éå½ç) æ¾å°ä¸ä¸ªåå« "method" çå,ç¶åæ§è¡å®.

A horse is a horse, of course of course -- or is it? é©¬å°±æ¯é©¬ââççæ¯è¿æ ·å?

æä»¬ä» "Animal" å "Horse" ç±»çä»£ç å¼å§:

{ package Animal;
sub speak {
my $class = shift;
print "a $class goes ", $class->sound, "!\n"
}
}
{ package Horse;
@ISA = qw(Animal);
sub sound { "neigh" }
}

è¿æ ·ä½¿å¾æä»¬è°ç¨ "Horse->speak"ï¼ä»èåä¸è°ç¨ "Animal::speak"ï¼ç¶åè°ç¨ "Horse::sound" æ¥è·å¾æå®çå£°é³ï¼è¾åºä¸º:

a Horse goes neigh!

my $name = "Mr. Ed";
my $talking = \$name;

ç°å¨ $talking æ¯æåå®ä¾ç¹ææ°æ®( $name )çå¼ç¨ãæè¿ä¸ªå¼ç¨åæçæ- £çå®ä¾çæ¯ä¸ä¸ªç¹æ®çæä½ç¬¦,å«å "bless":

bless $talking, Horse;

Invoking an instance method è°ç¨å®ä¾æ¹æ³

my $noise = $talking->sound;

è¦è°ç¨ "sound", Perl é¦åæ³¨æå° $talking æ¯ä¸ä¸ª blessed å¼ç¨ (å æ- ¤æ¯ä¸ä¸ªå®ä¾). å®ä¼æé ä¸ä¸ªåæ°åè¡¨, ç°å¨åªæ $talking. (å¨åé¢æä»¬ä¼çå°åæ°ä»¬å¨å®ä¾åéä¹å, ä¸ä½¿ç¨ç±»æ¶ç¸ä¼¼.)

Horse::sound($talking)

Accessing the instance data è®¿é®å®ä¾æ°æ®

{ package Horse;
@ISA = qw(Animal);
sub sound { "neigh" }
sub name {
my $self = shift;
$$self;
}
}

ç°å¨,æä»¬è°ç¨åå:

print $talking->name, " says ", $talking->sound, "\n";

å¨ "Horse::name" ä¸, @_ æ°ç»ä»å«æ $talking, shift å° $talking èµç»äº $self. (ä¼ ç»ä¸æä»¬å¨å¤çå®ä¾æ¹æ³æ¶æ»æ¯æç¬¬ä¸ä¸ªåç´ èµç» $self, æä»¥ä½ ä¹åºè¯¥è¿ä¹å, é¤éä½ æä¸è¿æ ·åçååçç±.) ç¶å, $self è¢«æ éå,æä¸º "Mr. Ed", è¿å°±è¡äº. è¾åºæ¯:

Mr. Ed says neigh.

How to build a horse å¦ä½åå»ºä¸å¹é©¬

{ package Horse;
@ISA = qw(Animal);
sub sound { "neigh" }
sub name {
my $self = shift;
$$self;
}
sub named {
my $class = shift;
my $name = shift;
bless \$name, $class;
}
}

ç°å¨,æä»¬å¯ä»¥ç¨ "named" æ¹æ³åå»ºä¸å¹é©¬:

my $talking = Horse->named("Mr. Ed");

æ³¨æå°æä»¬æåå°äºç±»æ¹æ³, æä»¥ä¼ éç» "Horse::named" çä¸¤ä¸ªåæ°æ¯ "Horse" å "Mr. Ed". "bless" æä½ç¬¦ä¸ä»å° $name å®ä¾å, ä¸å°æå $name çå¼ç¨ä½ä¸ºè¿åå¼è¿å. è¿æ ·, æä»¬å°±åå»ºäºä¸å¹é©¬.

Inheriting the constructor ç»§æ¿æé å¨

{ package Animal;
sub speak {
my $class = shift;
print "a $class goes ", $class->sound, "!\n"
}
sub name {
my $self = shift;
$$self;
}
sub named {
my $class = shift;
my $name = shift;
bless \$name, $class;
}
}
{ package Horse;
@ISA = qw(Animal);
sub sound { "neigh" }
}

å¥½äº, ä½æ¯ä»¥å®ä¾è°ç¨ "speak" ä¼äº§çä»ä¹ç»æå¢?

my $talking = Horse->named("Mr. Ed");
$talking->speak;

æä»¬å¾å°çæ¯:

a Horse=SCALAR(0xaca42ac) goes neigh!

Making a method work with either classes or instances ä½¿æ¹æ³åæ¶æ¯æç±»åå®ä¾

sub name {
my $either = shift;
ref $either
? $$either # it’s an instance, return name
: "an unnamed $either"; # it’s a class, return generic
}

my $talking = Horse->named("Mr. Ed");
print Horse->name, "\n"; # prints "an unnamed Horse\n"
print $talking->name, "\n"; # prints "Mr Ed.\n"

æä»¬å¯ä»¥æ¹å "speak" :

sub speak {
my $either = shift;
print $either->name, " goes ", $either->sound, "\n";
}

è "sound" æ¬æ¥å°±å¯ä»¥å·¥ä½. é£ä¹ç°å¨å°±ä¸åå®æäº!

Adding parameters to a method ç»æ¹æ³å åæ°

{ package Animal;
sub named {
my $class = shift;
my $name = shift;
bless \$name, $class;
}
sub name {
my $either = shift;
ref $either
? $$either # it’s an instance, return name
: "an unnamed $either"; # it’s a class, return generic
}
sub speak {
my $either = shift;
print $either->name, " goes ", $either->sound, "\n";
}
sub eat {
my $either = shift;
my $food = shift;
print $either->name, " eats $food.\n";
}
}
{ package Horse;
@ISA = qw(Animal);
sub sound { "neigh" }
}
{ package Sheep;
@ISA = qw(Animal);
sub sound { "baaaah" }
}

è¯è¯å§:

my $talking = Horse->named("Mr. Ed");
$talking->eat("hay");
Sheep->eat("grass");

è¾åºä¸º:

Mr. Ed eats hay.
an unnamed Sheep eats grass.

Animal::eat($talking, "hay");

More interesting instances æ´å¤æè¶£çå®ä¾

my $bad = bless { Name => "Evil", Color => "black" }, Sheep;

é£ä¹ "$bad->{Name}" æ¯ "Evil", "$bad->{Color}" æ¯ "black". ä½æ¯æä»¬æ³éè¿ "$bad->name" ååç»µç¾çååname, è¿æç¹çé®é¢,å ä¸ºç°å¨å®ææä¸ä¸ªæ éå¼ç¨. å«æå¿,å ä¸ºä¿®æ£å®å¾ç®å:

## in Animal
sub name {
my $either = shift;
ref $either ?
$either->{Name} :
"an unnamed $either";
}

"named" å½ç¶è¿æ¯åå»ºæ éçç»µç¾, å¦ä¸ä¿®æ£å°±å¥½äº:

## in Animal
sub named {
my $class = shift;
my $name = shift;
my $self = { Name => $name, Color => $class->default_color };
bless $self, $class;
}

## in Sheep
sub default_color { "white" }

## in Animal
sub default_color { "brown" }

ç°å¨, å ä¸ºåªæ "name" å "named" ä¸å¯¹è±¡ç "ç»æï¼structure" ç¸å³, å¶ä½çé¨åå¯ä»¥ä¿æä¸å, æä»¥ "speak" å·¥ä½æ£å¸¸.

## in Animal
sub color {
$_[0]->{Color}
}
sub set_color {
$_[0]->{Color} = $_[1];
}

my $talking = Horse->named("Mr. Ed");
$talking->set_color("black-and-white");
print $talking->name, " is colored ", $talking->color, "\n";

ç»ææ¯:

Mr. Ed is colored black-and-white

Summary æ»ç»

ç°å¨æä»¬è®²äºç±»æ¹æ³,æé å¨,å®ä¾æ¹æ³,å®ä¾æ°æ®,çè³è¿æååå¨(accessor). ä½æ¯è¿äºè¿ä»ä»æ¯å¼å§. æä»¬è¿æ²¡æè®²å°ä»¥ä¸¤ä¸ªå½æ° getters,setters å½¢å¼åºç°çååå¨ï¼ææå¨(destructor),é´æ¥å¯¹è±¡(indirect object notation),åç±»(subclasses that add instance data),per-class data,éè½½(overloading),"isa" å "can" æµè¯,å¬å±ç±»("UNIVERSAL" class),ç- ç. è¿æå¾å¶å®ææ¡£å»è®²è§£äº. æ è®ºå¦ä½,å¸ææ¬æä½¿ä½ å¯¹å¯¹è±¡ææäºè§£.

COPYRIGHT

Copyright (c) 1999, 2000 by Randal L. Schwartz and Stonehenge Consulting Services, Inc. Permission is hereby granted to distribute this document intact with the Perl distribution, and in accordance with the licenses of the Perl distribution; derived documents must include this copyright notice intact.

Portions of this text have been derived from Perl Training materials originally appearing in the Packages, References, Objects, and Modules course taught by instructors for Stonehenge Consulting Services, Inc. and used with permission.

Portions of this text have been derived from materials originally appearing in Linux Magazine and used with permission.

ä¸æçç»´æ¤äºº

redcandle <redcandle51@chinaren.com>

ä¸æçææ°æ´æ°

2001å¹´12æ9æ¥æææ¥

ä¸ææåé¡µç¿»è¯è®¡å

http://cmpp.linuxforum.net

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æ¬é¡µé¢ä¸æçç±ä¸æ man æåé¡µè®¡åæä¾ã
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PERLBOOT

NAME

DESCRIPTION æè¿°

SEE ALSO åè§

COPYRIGHT

ä¸æçç»´æ¤äºº

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