Enum Json

pub enum Json {
    Null,
    Bool(bool),
    Num(f64),
    Str(String),
    Arr(Vec<Json>),
    Obj(BTreeMap<String, Json>),
}

A JSON value held in memory, as the catalog manipulates it between the file and the model.

Variants

Null

The null literal, which the catalog uses for an absent or unknown field.

Bool(bool)

The true and false literals.

Num(f64)

A number: JSON knows only one numeric type, kept here as a double.

Str(String)

A text string, already unescaped: the characters it denotes, not its written form.

Arr(Vec<Json>)

An ordered sequence of values, the JSON array; a table of the schema is one of these.

Obj(BTreeMap<String, Json>)

A set of key/value pairs, kept sorted by key so that two writes give the same bytes.

Implementations

impl Json

pub fn obj() -> Json

Opens an empty object, the starting point for building a row field by field.

pub fn set(&mut self, key: &str, value: Json)

Adds or replaces a field. The call is silently ignored when the value is not an object.

pub fn get(&self, key: &str) -> Option<&Json>

Looks up a field by name; absent key and non-object alike give None, without failing.

pub fn as_str(&self) -> Option<&str>

Borrows the text of a string value, with no copy; anything else gives None.

pub fn as_string(&self) -> Option<String>

Same reading as Json::as_str, copied out for a caller that needs to keep the text.

pub fn as_f64(&self) -> Option<f64>

Reads a number as stored, with no conversion or rounding.

pub fn as_u64(&self) -> Option<u64>

Reads an integral, finite count in the u64 range. Fractional and out-of-range values are refused instead of being rounded or clamped.

pub fn as_u32(&self) -> Option<u32>

Same reading as Json::as_u64, narrowed for the small counters of the schema such as a year or a track number.

pub fn as_bool(&self) -> Option<bool>

Reads a boolean value; a 0 or a "true" string is not accepted as one.

pub fn as_arr(&self) -> Option<&[Json]>

Borrows the elements of an array, the usual way to walk over the rows of a table.

pub fn field_str(&self, key: &str) -> Option<String>

Direct access to a typed field, tolerating a missing key.

pub fn field_u64(&self, key: &str) -> Option<u64>

Reads a field as a count, absent or unusable giving None.

pub fn field_u32(&self, key: &str) -> Option<u32>

Reads a field as a small count, absent or unusable giving None.

pub fn field_f64(&self, key: &str) -> Option<f64>

Reads a numeric field that may be fractional.

pub fn field_optional_bool(&self, key: &str) -> Option<bool>

Reads a boolean field, None when it is absent or of another type.

Distinct from Json::field_bool, which answers false for both: an imported measurement that was never taken is not a measurement that came out negative.

pub fn field_bool(&self, key: &str) -> bool

Reads a flag, where an absent field means false: an older catalog that predates the flag is read without special handling.

impl Json

pub fn to_string_compact(&self) -> String

Serializes to compact JSON.

pub fn to_string_pretty(&self) -> String

Serializes to indented JSON, easier to inspect by hand.

Trait Implementations

impl Clone for Json

fn clone(&self) -> Json

Returns a duplicate of the value.

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

Performs copy-assignment from source.

impl Debug for Json

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

Formats the value using the given formatter.

impl From<&str> for Json

fn from(s: &str) -> Json

Converts to this type from the input type.

impl<T: Into<Json>> From<Option<T>> for Json

fn from(v: Option<T>) -> Json

Converts to this type from the input type.

impl From<String> for Json

fn from(s: String) -> Json

Converts to this type from the input type.

impl<T: Into<Json>> From<Vec<T>> for Json

fn from(v: Vec<T>) -> Json

Converts to this type from the input type.

impl From<bool> for Json

fn from(b: bool) -> Json

Converts to this type from the input type.

impl From<f64> for Json

fn from(n: f64) -> Json

Converts to this type from the input type.

impl From<i64> for Json

fn from(n: i64) -> Json

Converts to this type from the input type.

impl From<u32> for Json

fn from(n: u32) -> Json

Converts to this type from the input type.

impl From<u64> for Json

fn from(n: u64) -> Json

Converts to this type from the input type.

impl From<usize> for Json

fn from(n: usize) -> Json

Converts to this type from the input type.

impl PartialEq for Json

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

Tests for self and other values to be equal, and is used by ==.

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

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl StructuralPartialEq for Json