Struct Reader 

pub struct Reader { /* private fields */ }

JsonReader provides a simple, cursor-based API for parsing a JSON DOM.

It is similar, in spirit, to the XML Reader API.

The cursor is moved by the json_reader_read_* and the json_reader_end_* functions. You can enter a JSON object using ReaderExt::read_member() with the name of the object member, access the value at that position, and move the cursor back one level using ReaderExt::end_member(); arrays work in a similar way, using ReaderExt::read_element() with the index of the element, and using ReaderExt::end_element() to move the cursor back.

Using JsonReader

⚠️ The following code is in c ⚠️

g_autoptr(JsonParser) parser = json_parser_new ();

// str is defined elsewhere and contains:
// { "url" : "http://www.gnome.org/img/flash/two-thirty.png", "size" : [ 652, 242 ] }
json_parser_load_from_data (parser, str, -1, NULL);

g_autoptr(JsonReader) reader = json_reader_new (json_parser_get_root (parser));

// Enter the "url" member of the object
json_reader_read_member (reader, "url");
  const char *url = json_reader_get_string_value (reader);
  // url now contains "http://www.gnome.org/img/flash/two-thirty.png"
  json_reader_end_member (reader);

// Enter the "size" member of the object
json_reader_read_member (reader, "size");
  // Enter the first element of the array
  json_reader_read_element (reader, 0);
    int width = json_reader_get_int_value (reader);
    // width now contains 652
    json_reader_end_element (reader);
  // Enter the second element of the array
  json_reader_read_element (reader, 1);
    int height = json_reader_get_int_value (reader);
    // height now contains 242
    json_reader_end_element (reader);
  json_reader_end_member (reader);

Error handling

In case of error, JsonReader will be set in an error state; all subsequent calls will simply be ignored until a function that resets the error state is called, e.g.:

⚠️ The following code is in c ⚠️

// ask for the 7th element; if the element does not exist, the
// reader will be put in an error state
json_reader_read_element (reader, 6);

// in case of error, this will return NULL, otherwise it will
// return the value of the element
str = json_reader_get_string_value (value);

// this function resets the error state if any was set
json_reader_end_element (reader);

If you want to detect the error state as soon as possible, you can use ReaderExt::error():

⚠️ The following code is in c ⚠️

// like the example above, but in this case we print out the
// error immediately
if (!json_reader_read_element (reader, 6))
  {
    const GError *error = json_reader_get_error (reader);
    g_print ("Unable to read the element: %s", error->message);
  }

Properties

root

The root of the JSON tree that the reader should read.

Readable | Writeable | Construct

Implements

ReaderExt, [trait@glib::ObjectExt]

GLib type: GObject with reference counted clone semantics.

Implementations

impl Reader

pub const NONE: Option<&'static Reader> = None

pub fn new(node: Option<&Node>) -> Reader

Creates a new reader.

You can use this object to read the contents of the JSON tree starting from the given node.

node

the root node

Returns

the newly created reader

pub fn builder() -> ReaderBuilder

Creates a new builder-pattern struct instance to construct Reader objects.

This method returns an instance of ReaderBuilder which can be used to create Reader objects.

Trait Implementations

impl Clone for Reader

fn clone(&self) -> Self

Makes a clone of this shared reference.

This increments the strong reference count of the object. Dropping the object will decrement it again.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for Reader

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl Default for Reader

fn default() -> Self

Returns the “default value” for a type.

impl Eq for Reader

impl HasParamSpec for Reader

type ParamSpec = ParamSpecObject

type SetValue = Reader

Preferred value to be used as setter for the associated ParamSpec.

type BuilderFn = fn(&str) -> ParamSpecObjectBuilder<'_, Reader>

fn param_spec_builder() -> Self::BuilderFn

impl Hash for Reader

fn hash<H>(&self, state: &mut H)

where H: Hasher,

Hashes the memory address of this object.

fn hash_slice<H>(data: &[Self], state: &mut H)

where H: Hasher, Self: Sized,

Feeds a slice of this type into the given Hasher.

impl Ord for Reader

fn cmp(&self, other: &Self) -> Ordering

Comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn max(self, other: Self) -> Self

where Self: Sized,

Compares and returns the maximum of two values.

fn min(self, other: Self) -> Self

where Self: Sized,

Compares and returns the minimum of two values.

fn clamp(self, min: Self, max: Self) -> Self

where Self: Sized,

Restrict a value to a certain interval.

fn clamp_to<R>(self, range: R) -> Self

where Self: Sized, R: ClampBounds<Self>,

🔬This is a nightly-only experimental API. (clamp_to)

Restrict a value to a certain range.

impl ParentClassIs for Reader

type Parent = Object

impl<OT: ObjectType> PartialEq<OT> for Reader

fn eq(&self, other: &OT) -> bool

Equality for two GObjects.

Two GObjects are equal if their memory addresses are equal.

fn ne(&self, other: &Rhs) -> bool

Inequality operator !=.

impl<OT: ObjectType> PartialOrd<OT> for Reader

fn partial_cmp(&self, other: &OT) -> Option<Ordering>

Partial comparison for two GObjects.

Compares the memory addresses of the provided objects.

fn lt(&self, other: &Rhs) -> bool

Tests less than (for self and other) and is used by the < operator.

fn le(&self, other: &Rhs) -> bool

Tests less than or equal to (for self and other) and is used by the <= operator.

fn gt(&self, other: &Rhs) -> bool

Tests greater than (for self and other) and is used by the > operator.

fn ge(&self, other: &Rhs) -> bool

Tests greater than or equal to (for self and other) and is used by the >= operator.

impl StaticType for Reader

fn static_type() -> Type

Returns the type identifier of Self.