VariantBuilder

class VariantBuilder(**kwargs)

A utility type for constructing container-type Variant instances.

This is an opaque structure and may only be accessed using the following functions.

VariantBuilder is not threadsafe in any way. Do not attempt to access it from more than one thread.

Constructors

class VariantBuilder

classmethod new(type: VariantType) → VariantBuilder

Allocates and initialises a new VariantBuilder.

You should call unref() on the return value when it is no longer needed. The memory will not be automatically freed by any other call.

In most cases it is easier to place a VariantBuilder directly on the stack of the calling function and initialise it with init().

Added in version 2.24.

Parameters:

type – a container type

Methods

class VariantBuilder

add_value(value: Variant) → None

Adds value to builder.

It is an error to call this function in any way that would create an inconsistent value to be constructed. Some examples of this are putting different types of items into an array, putting the wrong types or number of items in a tuple, putting more than one value into a variant, etc.

If value is a floating reference (see ref_sink()), the builder instance takes ownership of value.

Added in version 2.24.

Parameters:

value – a Variant

close() → None

Closes the subcontainer inside the given builder that was opened by the most recent call to open().

It is an error to call this function in any way that would create an inconsistent value to be constructed (ie: too few values added to the subcontainer).

Added in version 2.24.

Returns:

True on success, False if there was an error.

end() → Variant

Ends the builder process and returns the constructed value.

It is not permissible to use builder in any way after this call except for reference counting operations (in the case of a heap-allocated VariantBuilder) or by reinitialising it with init() (in the case of stack-allocated). This means that for the stack-allocated builders there is no need to call clear() after the call to end().

It is an error to call this function in any way that would create an inconsistent value to be constructed (ie: insufficient number of items added to a container with a specific number of children required). It is also an error to call this function if the builder was created with an indefinite array or maybe type and no children have been added; in this case it is impossible to infer the type of the empty array.

Added in version 2.24.

open(type: VariantType) → None

Opens a subcontainer inside the given builder. When done adding items to the subcontainer, close() must be called. type is the type of the container: so to build a tuple of several values, type must include the tuple itself.

It is an error to call this function in any way that would cause an inconsistent value to be constructed (ie: adding too many values or a value of an incorrect type).

Example of building a nested variant:

GVariantBuilder builder;
guint32 some_number = get_number ();
g_autoptr (GHashTable) some_dict = get_dict ();
GHashTableIter iter;
const gchar *key;
const GVariant *value;
g_autoptr (GVariant) output = NULL;

g_variant_builder_init (&builder, G_VARIANT_TYPE ("(ua{sv})"));
g_variant_builder_add (&builder, "u", some_number);
g_variant_builder_open (&builder, G_VARIANT_TYPE ("a{sv}"));

g_hash_table_iter_init (&iter, some_dict);
while (g_hash_table_iter_next (&iter, (gpointer *) &key, (gpointer *) &value))
  {
    g_variant_builder_open (&builder, G_VARIANT_TYPE ("{sv}"));
    g_variant_builder_add (&builder, "s", key);
    g_variant_builder_add (&builder, "v", value);
    g_variant_builder_close (&builder);
  }

g_variant_builder_close (&builder);

output = g_variant_builder_end (&builder);

Added in version 2.24.

Parameters:

type – the VariantType of the container

Returns:

a new file descriptor, or -1 if an error occurred. The return value can be used exactly like the return value from open().