Error when using WWW::Mechanize

coderman9 has asked for the wisdom of the Perl Monks concerning the following question:

So, I'm trying to automate the process of buying something on amazon (its part of a larger project). To do that I'm using WWW::Mechanize. But I keep getting this error "Can't call method "header" on an undefined value at /usr/local/share/perl5/WWW/Mechanize.pm line 2566." No clue what's going on, but here's my code. I looked at line 2566, but am not sure what is happening, since I'm not using that method (at least I don't think I am).

use strict;
use WWW::Mechanize;
use Crypt::SSLeay;

#initialization
my $loginPage="https://www.amazon.com/ap/signin?_encoding=UTF8&openid.
+assoc_handle=amazon_checkout_us&openid.claimed_id=http%3A%2F%2Fspecs.
+openid.net%2Fauth%2F2.0%2Fidentifier_select&openid.identity=http%3A%2
+F%2Fspecs.openid.net%2Fauth%2F2.0%2Fidentifier_select&openid.mode=che
+ckid_setup&openid.ns=http%3A%2F%2Fspecs.openid.net%2Fauth%2F2.0&openi
+d.ns.pape=http%3A%2F%2Fspecs.openid.net%2Fextensions%2Fpape%2F1.0&ope
+nid.pape.max_auth_age=0&openid.return_to=https%3A%2F%2Fwww.amazon.com
+%2Fgp%2Fbuy%2Fsignin%2Fhandlers%2Fcontinue.html%3Fie%3DUTF8%26eGCApp%
+3D%26hasWorkingJavascript%3D0%26isEGCOrder%3D0%26oldCustomerId%3D%26o
+ldPurchaseId%3D%26preInitiateCustomerId%3D%26purchaseInProgress%3D%26
+siteDesign%3D&pageId=amazon_checkout_us&showRmrMe=0&siteState=isRegul
+arCheckout.1|IMBMsgs.|isRedirect.0";
my $addToCart="http://www.amazon.com/gp/product/handle-buy-box/ref=dp_
+start-bbf_1_glance";
#target
my $target="http://www.amazon.com/Effective-Java-Edition-Joshua-Bloch/
+dp/0321356683/ref=sr_1_2?ie=UTF8&qid=1386465356&sr=8-2&keywords=java"
+;
my $fileToWrite;

#login
my $email="something";
my $pass="somethingelse";

#browser object
my $mech=WWW::Mechanize->new(autocheck=>'1');
$mech->add_header(agent=>'Mozilla/5.0 (X11; Linux i686; rv:21.0) Gecko
+/20100101 Firefox/21.0');
$mech->cookie_jar
(
    HTTP::Cookies->new
    (
        'file'=>'/mnt/sdb1/porteus/cookies/amazonSessionId.lwp',
        'autosave'=>1,
    )
);

#main part, with dumping of statuses and content
$mech->get($target);
file("/file1.txt");
amazonSubmit($target);
file("/file2.txt");
amazonSubmit($addToCart);
file("/file3.txt");
login();
file("/file4.txt");

#subroutines
sub amazonSubmit()
{$mech->post(@_[0],
    [ 
        'type'=>'submit', 
        'value'=>'Go', 
        'class'=>'nav-submit-input', 
        'title'=>'Go',
    ]
    );
}

sub login()
{
    $mech->get($loginPage);
    $mech->set_visible($email, $pass);
    $mech->click_button('value'=>'"Sign in using our secure server"');
}    

sub file ()
{
    $fileToWrite=@_[0];
    open (FILEHANDLE, ">\$fileToWrite");
    print FILEHANDLE "$mech->content\n";
    print FILEHANDLE "$mech->status";
    close (FILEHANDLE);
}
[download]

Comment on Error when using WWW::Mechanize Download Code

Replies are listed 'Best First'.
Re: Error when using WWW::Mechanize by kschwab (Vicar) on Dec 15, 2013 at 15:16 UTC
You have other issues, but this particular one is triggered here: `sub login() { $mech->get($loginPage); $mech->set_visible($email, $pass); # # the original line, below, has double quotes nested # within single quotes # #$mech->click_button('value'=>'"Sign in using our secure server"') +; # no error if you remove them $mech->click_button('value'=>'Sign in using our secure server'); }` [download] For whatever reason, this "Can't call header.." error is what WWW:Mechanize does if you pass a value for a button that doesn't exist in the request to the click_button method. Seems like a bug to me. Indeed..it is. click_button does not check for zero matching inputs. Until that's fixed, you can trap the error yourself: `eval {$mech->click_button('value'=>'does not exist')}; if ($@) { warn("Can't click button\n"); }` [download]	[reply] [d/l] [select]
Re^2: Error when using WWW::Mechanize by coderman9 (Initiate) on Dec 15, 2013 at 21:34 UTC
Thanks a bunch. When reading the source code of the page I forgot that they would be using quotation marks also, so I was thinking that the value had the quotation marks in it. Thanks	[reply]
Re: Error when using WWW::Mechanize by Anonymous Monk on Dec 15, 2013 at 06:36 UTC
If I were you I'd learn scoping first because subs should take arguments (and most of the time return values, or throw exceptions) (Tutorials: Variable Scoping in Perl: the basics, Coping with Scoping , Mini-Tutorial: Perl's Memory Management, Lexical scoping like a fox,) ... then look into Net::Amazon, Net::Amazon::RemoteCart instead of scraping .... hope this helps	[reply]
Re^2: Error when using WWW::Mechanize by coderman9 (Initiate) on Dec 15, 2013 at 21:28 UTC
I do know functions fairly well from my work with C++, but you're right about the arguments and return values. Thanks for the module links too :)	[reply]
Re: Error when using WWW::Mechanize by Anonymous Monk on Feb 05, 2019 at 10:00 UTC
`$mech->get($loginPage); $mech->set_visible($email, $pass); $mech->click_button('value'=>'"Sign in using our secure server"'); }` [download] 2019-02-06 Athanasius added code tags	[reply] [d/l]