Perl教学(13)Perl的面向对象编程之五

coffee.pm代码如次：1 #2 # the coffee.pm file to illustrate inheritance.3 #4 package coffee;5 require exporter;6 require bean;7 @isa = qw(exporter, bean);8 @export = qw(setimports, declaremain, closemain);9 #10 # set item11 #12 sub setcoffeetype{13 my ($class,$name) = @_;14 $class->{'coffee'} = $name;15 print "set coffee type to $name \n";16 }17 #18 # constructor19 #20 sub new {21 my $type = shift;22 my $this = bean->new(); ##### <- look here!!! ####23 $this->{'coffee'} = 'instant'; # unless told otherwise24 bless $this, $type;25 return $this;26 }27 1; 第6行的require bean;语句包括了bean.pm文献和一切关系因变量，本领setcoffeetype()用来树立局域变量$class->{'coffee'}的值。在结构因变量new()中，$this指向bean.pm归来的隐姓埋名哈希表的南针，而不是在当地创造一个，底下两个语句辨别为创造各别的哈希表进而与bean.pm结构因变量创造的哈希表无干的情景和接受的情景：my $this = {}; #非接受my $this = $thesuperclass->new(); #接受底下代码演练怎样挪用接受的本领：1 #!/usr/bin/perl2 push (@inc,'pwd');3 use coffee;4 $cup = new coffee;5 print "\n -------------------- initial values ------------ \n";6 print "coffee: $cup->{'coffee'} \n";7 print "bean: $cup->{'bean'} \n";8 print "\n -------------------- change bean type ---------- \n";9 $cup->setbeantype('mixed');10 print "bean type is now $cup->{'bean'} \n";11 print "\n ------------------ change coffee type ---------- \n";12 $cup->setcoffeetype('instant');13 print "type of coffee: $cup->{'coffee'} \n"; 该代码的截止输入如次：-------------------- initial values ------------coffee: instantbean: colombian-------------------- change bean type ----------set bean to mixedbean type is now mixed ------------------ change coffee type ----------set coffee type to instanttype of coffee: instant 上述代码中，先输入东西创造时哈希表中索引为'bean'和'coffee'的值，而后挪用各分子因变量变换值后再输入。本领不妨有多个参数，此刻向coffee.pm模块减少因变量makecup()，代码如次：sub makecup {my ($class, $cream, $sugar, $dope) = @_;print "\n================================== \n"; print "making a cup \n";print "add cream \n" if ($cream);print "add $sugar sugar cubes\n" if ($sugar);print "making some really addictive coffee ;-) \n" if ($dope);print "================================== \n";} 此因变量可有三个参数，各别数量、值的参数爆发各别的截止，比方：1 #!/usr/bin/perl2 push (@inc,'pwd');3 use coffee;4 $cup = new coffee;5 #6 # with no parameters7 #8 print "\n calling with no parameters: \n";9 $cup->makecup;10 #11 # with one parameter12 #13 print "\n calling with one parameter: \n";14 $cup->makecup('1');15 #16 # with two parameters17 #18 print "\n calling with two parameters: \n";19 $cup->makecup(1,'2');20 #21 # with all three parameters22 #23 print "\n calling with three parameters: \n";24 $cup->makecup('1',3,'1'); 其截止输入如次：calling with no parameters:==================================making a cup==================================calling with one parameter:==================================making a cupadd cream==================================calling with two parameters:==================================making a cupadd creamadd 2 sugar cubes==================================calling with three parameters:==================================making a cupadd creamadd 3 sugar cubesmaking some really addictive coffee ;-)================================== 在此例中，因变量makecup()的参数既可为字符串也可为平头，处置截止沟通，你也不妨把这两种典型的数据处置辨别开。在对参数的处置中，不妨树立缺省的值，也不妨按照本质输出参数值的个数赋予各别处置。