show flow-control helpers and promises side by side in the cookbook

mojolicious · Oct 26, 2017 · 359e455 · 359e455
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commit 359e455
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Showing 3 changed files with 30 additions and 8 deletions.
diff --git a/lib/Mojo/IOLoop.pm b/lib/Mojo/IOLoop.pm
@@ -406,7 +406,7 @@ takes the same arguments as L<Mojo::IOLoop::Client/"connect">.
   my $delay = $loop->delay(sub {...});
   my $delay = $loop->delay(sub {...}, sub {...});
 
-Build L<Mojo::IOLoop::Delay> object to use as a promise or for flow-control.
+Build L<Mojo::IOLoop::Delay> object to use as a promise and/or for flow-control.
 Callbacks will be passed along to L<Mojo::IOLoop::Delay/"steps">.
 
   # Wrap continuation-passing style APIs with promises

diff --git a/lib/Mojo/IOLoop/Delay.pm b/lib/Mojo/IOLoop/Delay.pm
@@ -94,8 +94,7 @@ sub then {
 
 sub wait {
   my $self = shift;
-  return if $self->ioloop->is_running;
-  my $loop = $self->ioloop;
+  return if (my $loop = $self->ioloop)->is_running;
   $self->finally(sub { $loop->stop });
   $loop->start;
 }
@@ -157,11 +156,10 @@ sub _wrap {
 
   return sub {
     my @result;
-    unless (eval { @result = $cb->(@_); 1 }) {
-      $new->reject($@);
-    }
+    my $success = eval { @result = $cb->(@_); 1 };
+    if (!$success) { $new->reject($@) }
 
-    elsif (@result == 1 and blessed $result[0] and $result[0]->can('then')) {
+    elsif (@result == 1 && blessed $result[0] && $result[0]->can('then')) {
       $result[0]
         ->then(sub { $new->resolve(@_); () }, sub { $new->reject(@_); () });
     }

diff --git a/lib/Mojolicious/Guides/Cookbook.pod b/lib/Mojolicious/Guides/Cookbook.pod
@@ -1301,7 +1301,7 @@ synchronize multiple non-blocking requests.
   use Mojo::UserAgent;
   use Mojo::IOLoop;
 
-  # Synchronize non-blocking requests
+  # Synchronize non-blocking requests with flow-control helpers
   my $ua    = Mojo::UserAgent->new;
   my $delay = Mojo::IOLoop->delay(sub {
     my ($delay, $mojo, $minion) = @_;
@@ -1312,6 +1312,30 @@ synchronize multiple non-blocking requests.
   $ua->get('http://metacpan.org/search?q=minion' => $delay->begin);
   $delay->wait;
 
+If you plan on doing this a lot it might be worth wrapping your
+continuation-passing style APIs into promises, to make them easily composable.
+
+  use Mojo::UserAgent;
+  use Mojo::IOLoop;
+
+  # Synchronize non-blocking requests with promises
+  my $ua = Mojo::UserAgent->new;
+  sub get {
+    my $promise = Mojo::IOLoop->delay;
+    $ua->get(@_ => sub {
+      my ($ua, $tx) = @_;
+      $promise->resolve($tx);
+    });
+    return $promise;
+  }
+  my $mojo   = get('http://metacpan.org/search?q=mojo');
+  my $minion = get('http://metacpan.org/search?q=minion');
+  $mojo->all($minion)->then(sub {
+    my ($mojo, $minion) = @_;
+    say $mojo->result->dom->at('title')->text;
+    say $minion->result->dom->at('title')->text;
+  })->wait;
+
 The call to L<Mojo::IOLoop::Delay/"wait"> makes this code portable, it can now
 work inside an already running event loop or start one on demand.