Data::Edit::Struct - Edit a Perl structure addressed with a Data::DPath path
version 0.07
use Data::Edit::Struct qw[ edit ]; my $src = { foo => 9, bar => 2 }; my $dest = { foo => 1, bar => [22] }; edit( replace => { src => $src, spath => '/foo', dest => $dest, dpath => '/foo' } ); edit( insert => { src => $src, spath => '/bar', dest => $dest, dpath => '/bar' } ); # $dest = { foo => 9, bar => [ 2, 22 ] }
Data::Edit::Struct provides a high-level interface for editing data within complex data structures. Edit and source points are specified via Data::DPath paths.
The destination structure is the structure to be edited. If data are to be inserted into the structure, they are extracted from the source structure. See "Data Copying" for the copying policy.
The following actions may be performed on the destination structure:
shift - remove one or more elements from the front of an array
shift
pop - remove one or more elements from the end of an array
pop
splice - invoke splice on an array
splice
insert - insert elements into an array or a hash
insert
delete - delete array or hash elements
delete
replace - replace array or hash elements (and in the latter case keys)
replace
transform - transform elements
transform
Data::Edit::Struct operates on elements in the destination structure by following a Data::DPath path. For example, if
$src = { dogs => 'rule' }; $dest = { bar => [ 2, { cats => 'rule' }, 4 ] };
then a data path of
/bar/*[0]
identifies the first element in the bar array. That element may be treated either as a container or as an element (this is specified by the "dtype" option).
bar
In the above example, $dest->{bar}[0] resolves to a scalar, so by default it is treated as an element. However $dest->{bar[1]} resolves to a hashref. When operating on it, should it be treated as an opaque object, or as container? For example,
$dest->{bar}[0]
$dest->{bar[1]}
edit( insert => { src => $src, dest => $dest, dpath => '/bar/*[1]', } );
Should $src be inserted into element 2, as in
$src
$dest = { bar => [2, { cats => "rule", dogs => "rule" }, 4] };
or should it be inserted before element 2 in bar, as in?
$dest = { bar => [2, "dogs", "rule", { cats => "rule" }, 4] };
The first behavior treats it as a container, the second as an element. By default destination paths which resolve to hash or array references are treated as containers, so the above code generates the first behavior. To explicitly indicate how a path should be treated, use the dtype option. For example,
dtype
edit( insert => { src => $src, dest => $dest, dpath => '/bar/*[1]', dtype => 'element', } );
results in
Source structures may have the same ambiguity. In the above example, note that the contents of the hash in the source path are inserted, not the reference itself. This is because non-blessed references in sources are by default considered to be containers, and their contents are copied. To treat a source reference as an opaque element, use the "stype" option to specify it as such:
edit( insert => { src => $src, stype => 'element', dest => $dest, dpath => '/bar/*[1]', dtype => 'element', } );
which results in
$dest = { bar => [2, { dogs => "rule" }, { cats => "rule" }, 4] };
Note that dpath was set to element, otherwise edit would have attempted to insert the source hashref (not its contents) into the destination hash, which would have failed, as insertion into a hash requires a multiple of two elements (i.e., $key, $value).
dpath
edit
$key, $value
Data extracted from the source structure may undergo transformations prior to being inserted into the destination structure. There are several predefined transformations and the caller may specify a callback to perform their own.
Most of the transformations have to do with multiple values being returned by the source path. For example,
$src = { foo => [1], bar => [5], baz => [5] }; $spath = '/*/*[value == 5]';
would result in multiple extracted values:
(5, 5)
By default multiple values are not allowed, but a source transformation (specified by the sxfrm option ) may be used to change that behavior. The provided transforms are:
sxfrm
array
The values are assembled into an array. The stype parameter is used to determine whether that array is treated as a container or an element.
stype
hash
The items are assembled into a hash. The stype parameter is used to determine whether that hash is treated as a container or an element. Keys are derived from the data:
Keys for hash values will be their hash keys
Keys for array values will be their array indices
If there is a single value, a hash key may be specified via the key option to the sxfrm_args option.
key
sxfrm_args
iterate
The edit action is applied independently to each source value in turn.
If sxfrm is a code reference, it will be called to generate the source values. See "Source Callbacks" for more information.
If the sxfrm option is a code reference, it is called to generate the source values. It must return an array which contains references to the values (even if they are already references). For example, to return a hash:
my %src = ( foo => 1 ); return [ \\%hash ];
It is called with the arguments
$ctx
A "Data::DPath::Context" object representing the source structure.
$spath
The source path. Unless otherwise specified, this defaults to /, except when the source is not a plain array or plain hash, in which case the source is embedded in an array, and spath is set to /*[0].
/
spath
/*[0]
This is because "Data::DPath" requires a container to be at the root of the source structure, and anything other than a plain array or hash is most likely a blessed object or a scalar, both of which should be treated as elements.
$args
The value of the sxfrm_args option.
By default, copying of data from the source structure is done shallowly, e.g. references to arrays or hashes are not copied recursively. This may cause problems if further modifications are made to the destination structure which may, through references, alter the source structure.
For example, given the following input structures:
$src = { dogs => { say => 'bark' } }; $dest = { cats => { say => 'meow' } };
and this edit operation:
edit( insert => { src => $src, dest => $dest, } );
We get a destination structure that looks like this:
$dest = { cats => { say => "meow" }, dogs => { say => "bark" } };
But if later we change $dest,
$dest
# dogs are more excited now $dest->{dogs}{say} = 'howl';
the source structure is also changed:
$src = { dogs => { say => "howl" } };
To avoid this possible problem, Data::Edit::Struct can be passed the clone option, which will instruct it how to copy data.
Data::Edit::Struct
clone
Edit a data structure. The available actions are discussed below.
Destination structure parameters are:
dest
A reference to a structure or a Data::DPath::Context object.
A string representing the data path. This may result in multiple extracted values from the structure; the action will be applied to each in turn.
May be auto, element or container, to treat the extracted values either as elements or containers. If auto, non-blessed arrays and hashes are treated as containers.
auto
element
container
Some actions require a source structure; parameters related to that are:
src
A string representing the source path. This may result in multiple extracted values from the structure; the sxfrm option provides the context for how to interpret these values.
A transformation to be applied to the data extracted from the source. The available values are
See "Source Transformations" for more information.
This may be a boolean or a code reference. If a boolean, and true, "dclone" in Storable is used to clone the source structure. If set to a code reference, it is called with a reference to the structure to be cloned. It should return a reference to the cloned structure.
Actions may have additional parameters
Remove one or more elements from the end of an array. The destination structure must be an array. Additional parameters are:
length
The number of elements to remove. Defaults to 1.
1
Remove one or more elements from the front of an array. The destination structure must be an array. Additional parameters are:
Perform a splice operation on an array, e.g.
splice( @$dest, $offset, $length, @$src );
The $offset and $length parameters are provided by the offset and length options.
$offset
$length
offset
The destination structure may be an array or an array element. In the latter case, the actual offset passed to splice is the sum of the index of the array element and the value provided by the offset option.
A source structure is optional, and may be an array or a hash.
Insert a source structure into the destination structure. The result depends upon whether the point at which to insert is to be treated as a container or an element.
If the container is a hash, the source must be a container (either array or hash), and must contain an even number of elements. Each sequential pair of values is treated as a key, value pair.
If the container is an array, the source may be either a container or an element. The following options are available:
The offset into the array of the insertion point. Defaults to 0. See "anchor".
0
anchor
Indicates which end of the array the offset parameter is relative to. May be first or last. It defaults to first.
first
last
pad
If the array must be enlarged to accommodate the specified insertion point, fill the new values with this value. Defaults to undef.
undef
Indicates which side of the insertion point data will be inserted. May be either before or after. It defaults to before.
before
after
The insertion point must be an array value. The source may be either a container or an element. The following options are available:
Move the insertion point by this value.
Remove an array or hash value. If an array, the length option specifies the number of elements to remove, starting at that element. it defaults to 1.
Replace an array or hash element, or a hash key. The source data is always treated as an element. It takes the following options:
Indicates which part of a hash element to replace, either key or value. Defaults to value. If replacing the key and the source value is a reference, the value returned by Scalar::Util::refaddr will be used.
value
Transform an element via a user provided subroutine. It takes the following options:
callback_data
Arbitrary data to be passed to the callback.
callback
A code reference which will be called for each element. It is invoked as
$callback->( $point, $callback_data );
where $point is the Data::DPath::Point object representing the element, and $data is the value of the callback_data option.
$point
$data
Here's a silly example showing how to use the element object's attributes for a hash element:
$dest = { a => '1', 'b' => 2 }; edit( transform => { dest => $dest, dpath => '/*', callback => sub { my ( $point, $data ) = @_; ${ $point->ref } .= $point->attrs->key; }, }, );
With the result:
$dest = { a => "1a", b => "2b" };
Diab Jerius <djerius@cpan.org>
This software is Copyright (c) 2017 by Smithsonian Astrophysical Observatory.
This is free software, licensed under:
The GNU General Public License, Version 3, June 2007
To install Data::Edit::Struct, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Data::Edit::Struct
CPAN shell
perl -MCPAN -e shell install Data::Edit::Struct
For more information on module installation, please visit the detailed CPAN module installation guide.