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什么是事件編程？

舉個(gè)簡(jiǎn)單的例子，你瀏覽網(wǎng)頁(yè)的時(shí)候，你點(diǎn)擊一個(gè)圖片，蹭的彈出一個(gè)東西，你不點(diǎn)，那就在那里，等待一個(gè)人來(lái)點(diǎn)它。如果你寫過(guò)js，其實(shí)就是，你注冊(cè)了很多的時(shí)間比如click，dbclick，keybord，submit等，那么瀏覽器就起到幫我們?nèi)ケO(jiān)聽(tīng)這些事件的發(fā)生（Loop）。當(dāng)有對(duì)應(yīng)的事件發(fā)生的時(shí)候，我們也一般也設(shè)置了callback，比如onclick，onsubmit等，去響應(yīng)這些事件，這基本就是事件編程的一個(gè)縮影了。

2、perl AnyEvent中的watcher

在AnyEvent中有5中watcher，分別是IO，timer，signal, child, idle.

2.1 io watcher

代碼如下:

#!/usr/bin/perl

use AnyEvent;

my $cv = AnyEvent->condvar;

#open my $file , '<' , 'test.txt' or die "$!" ;

open F , '<' , 'test.txt' or die "$!" ;

my $io_watcher = AnyEvent->io (

fh => *F,

poll => 'r',

cb => sub {

chomp (my $input = sysread F ,my $buf ,1024); # read a line

warn "read: $buf\n" if $input >0 ; # output what has been read

#$cv->send if /quit/ ; # quit program if /quit/i

},

);

$cv->recv; # wait until user enters /quit/i

timer watcher

AnyEvent 的timer的一部分其實(shí)像javascript的setInterval :

代碼如下:

#!/usr/bin/perl

use 5.016;

use AnyEvent ;

my $cv = AnyEvent->condvar ;

my $w = AnyEvent->timer(

after => 0 , #多少秒之后觸發(fā)事件

interval => 2 , #多少秒觸發(fā)事件

cb => sub {

say AnyEvent->time ," ",AnyEvent->now ;

}

);

$cv->recv;

signal watcher

前面我們?cè)诘奈恼轮袑懙搅藀erl中對(duì)于信號(hào)的處理 《perl信號(hào)處理簡(jiǎn)單學(xué)習(xí)》，這里主要是AnyEvent中對(duì)于這些事件的處理。

代碼如下:

#!/usr/bin/perl

use 5.016;

use AnyEvent ;

#say for keys %SIG; 看一下又多少信號(hào)

my $cv = AnyEvent->condvar ;

my $w = AnyEvent->signal(

signal => 'INT',

cb => sub {

say AnyEvent->time ," ",AnyEvent->now ;

exit 1 ;

}

);

$cv->recv;

child watcher

代碼如下:

#!/usr/bin/perl

use AnyEvent;

my $done = AnyEvent->condvar;

my $pid = fork or exit 5;

my $w = AnyEvent->child (

pid => $pid,

cb => sub {

my ($pid, $status) = @_;

warn "pid $pid exited with status $status";

$done->send;

},

);

# do something else, then wait for process exit

$done->recv;

idle watcher

就是如果main loop在空閑的時(shí)候做些什么呢？

代碼如下:

#!/usr/bin/perl

use AnyEvent;

my @lines; # read data

my $idle_w;

$cv = AnyEvent->condvar;

my $io_w = AnyEvent->io (fh => \*STDIN, poll => 'r', cb => sub {

push @lines, scalar <STDIN>;

# start an idle watcher, if not already done

$idle_w ||= AnyEvent->idle (cb => sub {

# handle only one line, when there are lines left

if (my $line = shift @lines) {

print "handled when idle: $line";

} else {

# otherwise disable the idle watcher again

undef $idle_w;

}

});

});

$cv->recv;

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