NAME
Data::xPathLike - a xPath like processor for perl data-structures (hashes and arrays)!
VERSION
Version 0.101
Why we need another one
There are already some good approaches to xPath syntax, namely the Data::dPath and Data::Path. Nevertheless we still missing some of powerfull constructions as provided by xPath. Suppose, for example, we have an array of invoices with Total, Amount and Tax and need to check which one does not comply to the rule "Total = Amount * (1+Tax)".
For the data structure below we can easily achieve it with this code:
use Data::xPathLike;
use Data::Dumper;
($\,$,) = (qq|\n|, q|,|);
my $data = Data::xPathLike->data([
{invoice => {
Amount => 100,
Tax => 0.2,
Total => 120
}
},
{invoice => {
Amount => 200,
Tax => 0.15,
Total => 240
}
},
receipt =>{
}
]);
print Dumper $data->query(q$
//invoice[Total != Amount * (1 + Tax)]
$)->getvalues();The xPathLike uses the xPath 1.0 syntax to query any set of complex perl data structures, using keys or indexes for defining the path. Examples:
/0/invoice/Total
/2
/*/invoice[Total>100]/Total
//Tax
//Total[../Tax = .2]
//*[count(itens/*) > 1][1]
sum(//Total)Like as in xPath it's also possible to query a function.
SYNOPSIS
How to use it.
use strict;
use Data::xPathLike;
use Data::Dumper;
($\,$,) = ("\n",",");
my $d = {
drinks => {
q|Alcoholic beverage| => 'not allowed',
q|Soft drinks| => [qw|Soda Coke|]
},
food => {
fruit => [qw|bananas apples oranges pears|],
vegetables => [qw|potatoes carrots tomatoes|]
}
};
my $data = Data::xPathLike->data($d);
my $results = $data->query(q|/*/*/0|);
my @values = $results->getvalues();
print @values;
#Soda,bananas,potatoes
my $ref = $results->getref();
$$ref = 'Tonic';
print $d->{drinks}->{q|Soft drinks|}->[0];
#TonicTo get values we can invoke the getvalues ou getvalue methods to obtain a list/element matched. If what we need is to change the values we can use getrefs or getref methods to obtain a reference to the matched data-structures. The getref(s) methods always returns a reference to matched data-structure. If the matched element is a scalar a reference to that scalar is returned. If the matched element is a reference array (or hash) a reference to that reference is returned, so we can change it and not only nested data-structures.
DESCRIPTION
It looks for complex perl data-structures which match the xPathLike expression and returns a list of matched data-structures.
Like xPath it is possible to deal with any logical or arithmetic expressions, ex:
*{count(a) == count(c) / 2 * (1 + count(b)) or d}, or even query xPath functions ex:
count(//*)
name(//*[last()])
sum(//[*])Additionally some extensions are implemented to deal with perl data-structures, namely to choose between arrays and hashes.
Example:
Get all structures but only one which are arrays
//[*]Similarly to get all of hash structures, we can write
//{*}Besides that, some extra functions are also provide to check data type in predicates, ex:
//*[isScalar()]METHODS
The Data::xPathLike just provides two useful methods, compile and data. The first is used to compile a xPathLike expression and the second is used to prepare data to be queried.
Data::xPathLike methods
new()
Used only internally!!! Do nothing;
compile(xPathLikeString)
my $query = Data::xPathLike->compile('*'); #compile the query
my @values1 = $query->data({fruit => 'bananas'})->getvalues();
# @values1 = (bananas)
my @values2 = $query->data({
fruit => 'bananas',
vegetables => 'orions'
})->getvalues();
# @values2 = (bananas, orions)
my @values3 = $query->data({
food => {fruit => 'bananas'}
})->getvalues();
# @values3 = ({fruit => 'bananas'})The compile method receives a xPathLike string, compiles it and returns a Data::xPathLike::Data object. This is the prefered method to run the same query over several data-structures.
data(dataRef)
my $data = Data::xPathLike->data({
food => {
fruit => 'bananas',
vegetables => 'unions'
},
drinks => {
wine => 'Porto',
water => 'Evian'
}
});
my @values1 = $data->query('/*/*')->getvalues();
print @values1; # Evian,Porto,bananas,unions
my @values2 = $data->query('/*/wine')->getvalues();
print @values2; #Porto
#using a predicate, to get only first level entry which contains a fruit key
my @values3 = $data->query('/*[fruit]/*')->getvalues();
print @values3; #bananas,unions
#using another filter to return only elements which have the value matching
#a /an/ pattern
my @values4 = $data->query('/*/*[. ~ "an"]')->getvalues();
print @values4;# Evian,bananas
my @values5 = $data->query('//*[isScalar()]')->getvalues();
print @values5;#Evian,Porto,bananas,unions
The method data receives a hash (or array) reference and returns a Data::xPathLike::Compile object. This is the prefered method to run several query over same data.
Data::xPathLike::Data methods
data(data)
Executes the query over data and returns a Data::xPathLike::Results object
Data::xPathLike::Compiler methods
query(xPathLikeString)
Compile a xPathLike string, query the data and returns a Data::xPathLike::Results object
Data::xPathLike::Results methods
getrefs() Returns a list os references for each matched data;
getref() Returns a reference for first matched data;
getvalues() Returns a list of values for each matched data;
getvalue() Returns the value of first matched data;
xPath Compability
Unless some xPath functions, not yet implemented, and xPath axis preceding:: and following:: directions everything else is implemented. Probably buggly, sorry. I hope to fixe them as soon someone (?) identify them.
Supported axis
- self::
- child::
- parent::
- ancestor::
- ancestor-or-self::
- descendant::
- descendant-or-self::
- preceding-sibling::
- following::sibling::
Supported Functions
- count(path?)
- sum(path)
- name(path?)
- position(path?)
- last()
- not(expr)
- names(path?)*
- values(path?)*
- value(path?)*
(*) not a xPath 1.0 function.
names is like name but returns a list of names.
We don't support the text() funcions as we don't know what that should mean in perl data-structures context, but the value() and values() functions are provided to return the value/values of current context if path argument is missing or the value/values of matched data-structures. That/those value/values could be scalar(s) or hash/array reference(s).
Supported operators
The xPath supported operators are the following:
+, -, *, div, %, =, !=, (), "", '', +, -, ., .., /, //, ::, <, <=, >, >=, [], and, or
and
| (paths union)Addicionaly xPathLike also supports the following operators
eq, ne, lt, le, gt, ge and ~ The ~ is the matching operator
Support for data types
In xPathLike path expression, a digit step could mean a array index or a hash's key name. ex:
/a/0/bmay refere to a $d->{a}->[0]->{b} or to a $d->{a}->{0}->{b}. If a enforcement is required for select only array's index 0 the xPathLike expression should be
/a/[0]/bAnd similarly for hash' key '0'
/a/{0}/bThe curly bracket could also be useful to refere to keys with spaces or any special character. Some examples
/{two words as a keys}//{key with a / or a +}/*The curly and square brackets could also be used with axis and wildcard *. Examples:
//{*}
//[*]
//*/parent::[b]
//a//parent::{*}
//*[self::{*} = 3 or self::[*] > 10]
/1/[*][4]/child::[*][1]/{a}/following-sibling::*[last()]If a hash key is just a * the path expression is also posible using instead curly brackets, quotes (double or single)
//"*"/b
//a/'*'Inside curly brackets, or quotes a backslash is used to escape { or } if the step delimited by those characters and " when used inside doubles quotes or ' for single quotes delimitation,or escape itself. In any other situation is literaly interpreted
//"2\""
//'hash\'s key'
//{\{}/
//'2"'
//"hash\'s key"
//'{'
//{\\}
//"\\"
//'\\'AUTHOR
Isidro Vila Verde, <jvverde at gmail.com>
BUGS
Send email to <jvverde at gmail.com> with subject Data::xPathLike
SUPPORT
You can find documentation for this module with the perldoc command.
perldoc Data::xPathLikeLICENSE AND COPYRIGHT
Copyright 2013 Isidro Vila Verde.
This program is free software; you can redistribute it and/or modify it under the terms of the the Artistic License (2.0). You may obtain a copy of the full license at:
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