Module glib::variant [−][src]
Expand description
Variant
binding and helper traits.
Variant
is an immutable dynamically-typed generic
container. Its type and value are defined at construction and never change.
Variant
types are described by VariantType
“type strings”.
Although GVariant
supports arbitrarily complex types, this binding is
currently limited to the basic ones: bool
, u8
, i16
, u16
, i32
,
u32
, i64
, u64
, f64
, &str
/String
, and VariantDict
.
Examples
use glib::prelude::*; // or `use gtk::prelude::*;`
use glib::{Variant, FromVariant, ToVariant};
use std::collections::HashMap;
// Using the `ToVariant` trait.
let num = 10.to_variant();
// `is` tests the type of the value.
assert!(num.is::<i32>());
// `get` tries to extract the value.
assert_eq!(num.get::<i32>(), Some(10));
assert_eq!(num.get::<u32>(), None);
// `get_str` tries to borrow a string slice.
let hello = "Hello!".to_variant();
assert_eq!(hello.str(), Some("Hello!"));
assert_eq!(num.str(), None);
// `bytes` tries to borrow a byte array (GVariant type `ay`),
// rather than creating a deep copy which would be expensive for
// nontrivially sized byte arrays.
// The test data here is the zstd compression header, which
// stands in for arbitrary binary data (e.g. not UTF-8).
let bufdata = b"\xFD\x2F\xB5\x28";
let bufv = bufdata.to_variant();
assert_eq!(bufv.bytes().unwrap(), bufdata);
assert!(num.bytes().is_err());
// Variant carrying a Variant
let variant = Variant::from_variant(&hello);
let variant = variant.as_variant().unwrap();
assert_eq!(variant.str(), Some("Hello!"));
// Variant carrying an array
let array = ["Hello".to_variant(), "there!".to_variant()];
let variant = Variant::from_array::<&str>(&array);
assert_eq!(variant.n_children(), 2);
assert_eq!(variant.child_value(0).str(), Some("Hello"));
assert_eq!(variant.child_value(1).str(), Some("there!"));
// You can also convert from and to a Vec
let array = vec!["Hello", "there!"].to_variant();
assert_eq!(variant.n_children(), 2);
let vec = <Vec<String>>::from_variant(&array).unwrap();
assert_eq!(vec[0], "Hello");
// Conversion to and from HashMap is also possible
let mut map: HashMap<u16, &str> = HashMap::new();
map.insert(1, "hi");
map.insert(2, "there");
let variant = map.to_variant();
assert_eq!(variant.n_children(), 2);
let map: HashMap<u16, String> = HashMap::from_variant(&variant).unwrap();
assert_eq!(map[&1], "hi");
assert_eq!(map[&2], "there");
// And conversion to and from tuples.
let variant = ("hello", 42u16, vec![ "there", "you" ],).to_variant();
assert_eq!(variant.n_children(), 3);
assert_eq!(variant.type_().to_str(), "(sqas)");
let tuple = <(String, u16, Vec<String>)>::from_variant(&variant).unwrap();
assert_eq!(tuple.0, "hello");
assert_eq!(tuple.1, 42);
assert_eq!(tuple.2, &[ "there", "you"]);
// `Option` is supported as well, through maybe types
let variant = Some("hello").to_variant();
assert_eq!(variant.n_children(), 1);
let mut s = <Option<String>>::from_variant(&variant).unwrap();
assert_eq!(s.unwrap(), "hello");
s = None;
let variant = s.to_variant();
assert_eq!(variant.n_children(), 0);
let s = <Option<String>>::from_variant(&variant).unwrap();
assert!(s.is_none());
Structs
A Dictionary entry.
A generic immutable value capable of carrying various types.
Traits
Extracts a value.
Returns VariantType
of Self
.
Converts to Variant
.