Using Google APIs for Lattitude

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

Hi All
I've created the following script:

use strict;
use warnings;
use LWP::Simple; # from CPAN
use JSON qw( decode_json ); # from CPAN
#get my address
use LWP::UserAgent;
my $ua = LWP::UserAgent->new;

my $server_endpoint = "https://www.googleapis.com/geolocation/v1/geolo
+cate?key=MY API KEY";

# set custom HTTP request header fields
my $req = new HTTP::Request POST =>( $server_endpoint);
$req->header('content-type' => 'application/json');

# add POST data to HTTP request body
my $post_data = '{"homeMobileCountryCode" : 235,
"homeMobileNetworkCode" : 77,
"radioType" : "gsm",
"carrier" : "BT Group",
"considerIp" : "true"}';
$req->content($post_data);

my $resp = $ua->request($req);


  my $message = $resp->decoded_content;

 print "Received Reply:$message\n";
[download]

Which successfully prints

Received Reply:{
 "location": {
  "lat": 53.4232611,
  "lng": -1.0836272999999998
 },
 "accuracy": 901.0
}
[download]

What I need to do now is get the lat and lng values to use in a new script, but I just cant do it. I'm trying

my $lat = $message->{"location"}{"lat"};
[download]

but I get the error message

Can't use string ("{
 "location": {
  "lat": 53.423"...) as a HASH ref while "strict refs" in use at etc.e
+tc.
[download]

Please point me in the right direction

Comment on Using Google APIs for Lattitude Select or Download Code

Replies are listed 'Best First'.
Re: Using Google APIs for Lattitude by huck (Prior) on Jul 03, 2017 at 20:14 UTC
try adding this `use JSON; my $json=new JSON; my $unjson; eval{ $unjson=$json->allow_nonref->decode($message);} ; warn 'json decode error:'.$@ ."\n" if ($@); my $lat = $unjson->{"location"}{"lat"};` [download]	[reply] [d/l]
Re^2: Using Google APIs for Lattitude by stevieb (Canon) on Jul 03, 2017 at 21:27 UTC
Nice huck, but I'd just like to give you a tidbit... `$@` is an interesting variable. As soon as you go into an `eval`, you overwrite (clear) that var immediately. Worse, because of its nature, it could be set elsewhere even while you're in your `eval` call, rendering your use of it useless, or worse, confusing. For these reasons, base a `warn` or other activities on whether the `eval` caught a throw directly, not on `$@` which could be set somewhere else, even far away, that's not related even remotely to your check: `use JSON; my $json = new JSON; my $unjson; my $statement_ok = eval { $unjson = $json->allow_nonref->decode($message); 1; }; if (! $statement_ok){ # $@ can be interpolated ;) warn "json decode error: $@\n"; } my $lat = $unjson->{"location"}{"lat"};` [download] If `eval` catches an exception, the true (`1;`) will never be returned, rendering `$statement_ok` `undef`, allowing you act based on the result of the `eval`, not whether `$@` is set or not. You could further it a bit (untested): `my $ok = eval { foo(); 1; }; if (! $ok){ if ($@ =~ /internal error/){ warn "foo() fsck'd up!\n"; } else { warn "foo() fsck'd up, with unexpected err: $@\n"; } }` [download] Looking at Try::Tiny, it explains what I've said in detail. That module is a different approach to your excellent example.	[reply] [d/l] [select]
Re^2: Using Google APIs for Lattitude by mattpower (Initiate) on Jul 04, 2017 at 08:02 UTC
Huck Spot on worked like a treat, the main goal here is to use my pi to locate my phone, and if its a certain distance from home switch off my heating. I already have my heating controlled by the weather and if my solar panels are generating, this will enable me to reach the next step. Many Thanks	[reply]
Re: Using Google APIs for Lattitude by stevieb (Canon) on Jul 03, 2017 at 20:02 UTC
Hi mattpower, Please edit your question and use `<p></p>` tags around your sentences, and `<code></code>` tags around your code, any input data, and any expected output data.	[reply] [d/l] [select]