API reference - Class LayoutQuery

Notation used in Ruby API documentation

Module: db

Description: A layout query

Layout queries are the backbone of the "Search & replace" feature. Layout queries allow retrieval of data from layouts and manipulation of layouts. This object provides script binding for this feature. Layout queries are used by first creating a query object. Depending on the nature of the query, either execute or each can be used to execute the query. execute will run the query and return once the query is finished. execute is useful for running queries that don't return results such as "delete" or "with ... do" queries. each can be used when the results of the query need to be retrieved.

The each method will call a block a of code for every result available. It will provide a LayoutQueryIterator object that allows accessing the results of the query. Depending on the query, different attributes of the iterator object will be available. For example, "select" queries will fill the "data" attribute with an array of values corresponding to the columns of the selection.

Here is some sample code:

ly = RBA::CellView::active.layout
q = RBA::LayoutQuery::new("select cell.name, cell.bbox from *")
q.each(ly) do |iter|
  puts "cell name: #{iter.data[0]}, bounding box: #{iter.data[1]}"
end

The LayoutQuery class has been introduced in version 0.25.

Public constructors

new LayoutQuery ptrnew(string query)Creates a new query object from the given query string

Public methods

void_createEnsures the C++ object is created
void_destroyExplicitly destroys the object
[const]bool_destroyed?Returns a value indicating whether the object was already destroyed
[const]bool_is_const_object?Returns a value indicating whether the reference is a const reference
void_manageMarks the object as managed by the script side.
void_unmanageMarks the object as no longer owned by the script side.
[const,iter]LayoutQueryIteratoreach(const Layout ptr layout,
ExpressionContext ptr context = nil)
Executes the query and delivered the results iteratively.
voidexecute(Layout layout,
ExpressionContext ptr context = nil)
Executes the query
[const]string[]property_namesGets a list of property names available.

Deprecated methods (protected, public, static, non-static and constructors)

voidcreateUse of this method is deprecated. Use _create instead
voiddestroyUse of this method is deprecated. Use _destroy instead
[const]booldestroyed?Use of this method is deprecated. Use _destroyed? instead
[const]boolis_const_object?Use of this method is deprecated. Use _is_const_object? instead

Detailed description

_create

Signature: void _create

Description: Ensures the C++ object is created

Use this method to ensure the C++ object is created, for example to ensure that resources are allocated. Usually C++ objects are created on demand and not necessarily when the script object is created.

_destroy

Signature: void _destroy

Description: Explicitly destroys the object

Explicitly destroys the object on C++ side if it was owned by the script interpreter. Subsequent access to this object will throw an exception. If the object is not owned by the script, this method will do nothing.

_destroyed?

Signature: [const] bool _destroyed?

Description: Returns a value indicating whether the object was already destroyed

This method returns true, if the object was destroyed, either explicitly or by the C++ side. The latter may happen, if the object is owned by a C++ object which got destroyed itself.

_is_const_object?

Signature: [const] bool _is_const_object?

Description: Returns a value indicating whether the reference is a const reference

This method returns true, if self is a const reference. In that case, only const methods may be called on self.

_manage

Signature: void _manage

Description: Marks the object as managed by the script side.

After calling this method on an object, the script side will be responsible for the management of the object. This method may be called if an object is returned from a C++ function and the object is known not to be owned by any C++ instance. If necessary, the script side may delete the object if the script's reference is no longer required.

Usually it's not required to call this method. It has been introduced in version 0.24.

_unmanage

Signature: void _unmanage

Description: Marks the object as no longer owned by the script side.

Calling this method will make this object no longer owned by the script's memory management. Instead, the object must be managed in some other way. Usually this method may be called if it is known that some C++ object holds and manages this object. Technically speaking, this method will turn the script's reference into a weak reference. After the script engine decides to delete the reference, the object itself will still exist. If the object is not managed otherwise, memory leaks will occur.

Usually it's not required to call this method. It has been introduced in version 0.24.

create

Signature: void create

Description: Ensures the C++ object is created

Use of this method is deprecated. Use _create instead

Use this method to ensure the C++ object is created, for example to ensure that resources are allocated. Usually C++ objects are created on demand and not necessarily when the script object is created.

destroy

Signature: void destroy

Description: Explicitly destroys the object

Use of this method is deprecated. Use _destroy instead

Explicitly destroys the object on C++ side if it was owned by the script interpreter. Subsequent access to this object will throw an exception. If the object is not owned by the script, this method will do nothing.

destroyed?

Signature: [const] bool destroyed?

Description: Returns a value indicating whether the object was already destroyed

Use of this method is deprecated. Use _destroyed? instead

This method returns true, if the object was destroyed, either explicitly or by the C++ side. The latter may happen, if the object is owned by a C++ object which got destroyed itself.

each

Signature: [const,iter] LayoutQueryIterator each (const Layout ptr layout, ExpressionContext ptr context = nil)

Description: Executes the query and delivered the results iteratively.

The argument to the block is a LayoutQueryIterator object which can be asked for specific results.

The context argument allows supplying an expression execution context. This context can be used for example to supply variables for the execution. It has been added in version 0.26.

execute

Signature: void execute (Layout layout, ExpressionContext ptr context = nil)

Description: Executes the query

This method can be used to execute "active" queries such as "delete" or "with ... do". It is basically equivalent to iterating over the query until it is done.

The context argument allows supplying an expression execution context. This context can be used for example to supply variables for the execution. It has been added in version 0.26.

is_const_object?

Signature: [const] bool is_const_object?

Description: Returns a value indicating whether the reference is a const reference

Use of this method is deprecated. Use _is_const_object? instead

This method returns true, if self is a const reference. In that case, only const methods may be called on self.

new

Signature: [static] new LayoutQuery ptr new (string query)

Description: Creates a new query object from the given query string

Python specific notes:
This method is the default initializer of the object

property_names

Signature: [const] string[] property_names

Description: Gets a list of property names available.

The list of properties available from the query depends on the nature of the query. This method allows detection of the properties available. Within the query, all of these properties can be obtained from the query iterator using LayoutQueryIterator#get.