--- name: "Config::Model::WarpedNode" section: "3pm" platform: "linux" package: "libconfig-model-perl" version: "2.155-1" release: "Debian 13 (Trixie)" platforms: ["linux"] url: "https://new.carta.tech/Config::Model::WarpedNode" --- # Config::Model::WarpedNode(3pm) Node that change config class properties ## NAME Config::Model::WarpedNode - Node that change config class properties ## VERSION version 2.155 ## SYNOPSIS ``` use Config::Model; my $model = Config::Model->new; foreach (qw/X Y/) { $model->create_config_class( name => "Class$_", element => [ foo => {qw/type leaf value_type string/} ] ); } $model->create_config_class( name => "MyClass", element => [ master_switch => { type => 'leaf', value_type => 'enum', choice => [qw/cX cY/] }, 'a_warped_node' => { type => 'warped_node', warp => } follow => { ms => '! master_switch' }, rules => [ '$ms eq "cX"' => { config_class_name => 'ClassX' }, '$ms eq "cY"' => { config_class_name => 'ClassY' }, ] } }, ], ); my $inst = $model->instance(root_class_name => 'MyClass' ); my $root = $inst->config_root ; print "Visible elements: ",join(' ',$root->get_element_name),"\n" ; # Visible elements: master_switch $root->load( steps => 'master_switch=cX' ); print "Visible elements: ",join(' ',$root->get_element_name),"\n" ; # Visible elements: master_switch a_warped_node my $node = $root->grab('a_warped_node') ; print "a_warped_node class: ",$node->config_class_name,"\n" ; # a_warped_node class: ClassX $root->load( steps => 'master_switch=cY' ); print "a_warped_node class: ",$node->config_class_name,"\n" ; # a_warped_node class: ClassY ``` ## DESCRIPTION This class provides a way to change dynamically the configuration class (or some other properties) of a node. The changes are done according to the model declaration. This declaration specifies one (or several) leaf in the configuration tree that triggers the actual property change of the warped node. This leaf is also referred as *warp master*. When the warp master(s) value(s) changes, `"WarpedNode"` creates an instance of the new class required by the warp master. If the morph parameter is set, the values held by the old object are (if possible) copied to the new instance of the object using copy\_from method. Warped node can alter the following properties: ``` config_class_name level ``` ## Constructor `"WarpedNode"` should not be created directly. ## Warped node model declaration ### Parameter overview A warped node must be declared with the following parameters: - type Always set to `"warped_node"`. - follow Grab string leading to the `"Config::Model::Value"` warp master. See "Warp follow argument" in Config::Model::Warper for details. - morph boolean. If 1, `"WarpedNode"` tries to recursively copy the value from the old object to the new object using copy\_from method. When a copy is not possible, undef values are assigned to object elements. - rules Hash or array ref that specify the property change rules according to the warp master(s) value(s). See "Warp rules argument" in Config::Model::Warper for details on how to specify the warp master values (or combination of values). ### Effect declaration For a warped node, the effects are declared with these parameters: - **config\_class\_name** When requested by the warp master,the `"WarpedNode"` creates a new object of the type specified by this parameter: ``` XZ => { config_class_name => 'SlaveZ' } ``` Instead of a string, you can an array ref which contains the class name and constructor arguments : ``` XY => { config_class_name => ['SlaveY', foo => 'bar' ], }, ``` - **class** Specify a Perl class to implement the above config class. This Perl Class **must** inherit Config::Model::Node. ## Forwarded methods The following methods are forwarded to contained node: fetch\_element config\_class\_name get\_element\_name has\_element is\_element\_available element\_type load fetch\_element\_value get\_type get\_cargo\_type describe ## Methods ### name Return the name of the node (even if warped out). ### is\_accessible Returns true if the node hidden behind this warped node is accessible, i.e. the warp master have values so a node was warped in. ### get\_actual\_node Returns the node object hidden behind the warped node. Croaks if the node is not accessible. ### load\_data Parameters: `"( hash_ref )"` Load configuration data with a hash ref. The hash ref key must match the available elements of the node carried by the warped node. ## EXAMPLE ``` $model ->create_config_class ( element => [ tree_macro => { type => 'leaf', value_type => 'enum', choice => [qw/XX XY XZ ZZ/] }, bar => { type => 'warped_node', follow => '! tree_macro', morph => 1, rules => [ XX => { config_class_name => [ 'ClassX', 'foo' ,'bar' ]} XY => { config_class_name => 'ClassY'}, XZ => { config_class_name => 'ClassZ'} ] } ] ); ``` In the example above we see that: - • The 'bar' slot can refer to a `"ClassX"`, `"ClassZ"` or `"ClassY"` object. - • The warper object is the `"tree_macro"` attribute of the root of the object tree. - • When `"tree_macro"` is set to `"ZZ"`, `"bar"` is not available. Trying to access `"bar"` raises an exception. - • When `"tree_macro"` is changed from `"ZZ"` to `"XX"`, `"bar"` refers to a brand new `"ClassX"` object constructed with `"ClassX->new(foo => 'bar')"` - • Then, if `"tree_macro"` is changed from `"XX"` to `"XY"`, `"bar"` refers to a brand new `"ClassY"` object. But in this case, the object is initialized with most if not all the attributes of `"ClassX"`. This copy is done whenever `"tree_macro"` is changed. ## AUTHOR Dominique Dumont, (ddumont at cpan dot org) ## SEE ALSO Config::Model::Instance, Config::Model, Config::Model::HashId, Config::Model::ListId, Config::Model::AnyThing, Config::Model::Warper, Config::Model::WarpedNode, Config::Model::Value ## AUTHOR Dominique Dumont ## COPYRIGHT AND LICENSE This software is Copyright (c) 2005-2022 by Dominique Dumont. This is free software, licensed under: ``` The GNU Lesser General Public License, Version 2.1, February 1999 ```