Enum serde_json::value::Value [−][src]
pub enum Value { Null, Bool(bool), Number(Number), String(String), Array(Vec<Value>), Object(Map<String, Value>), }
Represents any valid JSON value.
See the serde_json::value
module documentation for usage examples.
Variants
Represents a JSON null value.
let v = json!(null);
Bool(bool)
Represents a JSON boolean.
let v = json!(true);
Number(Number)
Represents a JSON number, whether integer or floating point.
let v = json!(12.5);
String(String)
Represents a JSON string.
let v = json!("a string");
Represents a JSON array.
let v = json!(["an", "array"]);
Represents a JSON object.
By default the map is backed by a BTreeMap. Enable the preserve_order
feature of serde_json to use IndexMap instead, which preserves
entries in the order they are inserted into the map. In particular, this
allows JSON data to be deserialized into a Value and serialized to a
string while retaining the order of map keys in the input.
let v = json!({ "an": "object" });
Implementations
impl Value
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pub fn get<I: Index>(&self, index: I) -> Option<&Value>
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Index into a JSON array or map. A string index can be used to access a value in a map, and a usize index can be used to access an element of an array.
Returns None
if the type of self
does not match the type of the
index, for example if the index is a string and self
is an array or a
number. Also returns None
if the given key does not exist in the map
or the given index is not within the bounds of the array.
let object = json!({ "A": 65, "B": 66, "C": 67 }); assert_eq!(*object.get("A").unwrap(), json!(65)); let array = json!([ "A", "B", "C" ]); assert_eq!(*array.get(2).unwrap(), json!("C")); assert_eq!(array.get("A"), None);
Square brackets can also be used to index into a value in a more concise
way. This returns Value::Null
in cases where get
would have returned
None
.
let object = json!({ "A": ["a", "á", "à"], "B": ["b", "b́"], "C": ["c", "ć", "ć̣", "ḉ"], }); assert_eq!(object["B"][0], json!("b")); assert_eq!(object["D"], json!(null)); assert_eq!(object[0]["x"]["y"]["z"], json!(null));
pub fn get_mut<I: Index>(&mut self, index: I) -> Option<&mut Value>
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Mutably index into a JSON array or map. A string index can be used to access a value in a map, and a usize index can be used to access an element of an array.
Returns None
if the type of self
does not match the type of the
index, for example if the index is a string and self
is an array or a
number. Also returns None
if the given key does not exist in the map
or the given index is not within the bounds of the array.
let mut object = json!({ "A": 65, "B": 66, "C": 67 }); *object.get_mut("A").unwrap() = json!(69); let mut array = json!([ "A", "B", "C" ]); *array.get_mut(2).unwrap() = json!("D");
pub fn is_object(&self) -> bool
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Returns true if the Value
is an Object. Returns false otherwise.
For any Value on which is_object
returns true, as_object
and
as_object_mut
are guaranteed to return the map representation of the
object.
let obj = json!({ "a": { "nested": true }, "b": ["an", "array"] }); assert!(obj.is_object()); assert!(obj["a"].is_object()); // array, not an object assert!(!obj["b"].is_object());
pub fn as_object(&self) -> Option<&Map<String, Value>>
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If the Value
is an Object, returns the associated Map. Returns None
otherwise.
let v = json!({ "a": { "nested": true }, "b": ["an", "array"] }); // The length of `{"nested": true}` is 1 entry. assert_eq!(v["a"].as_object().unwrap().len(), 1); // The array `["an", "array"]` is not an object. assert_eq!(v["b"].as_object(), None);
pub fn as_object_mut(&mut self) -> Option<&mut Map<String, Value>>
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If the Value
is an Object, returns the associated mutable Map.
Returns None otherwise.
let mut v = json!({ "a": { "nested": true } }); v["a"].as_object_mut().unwrap().clear(); assert_eq!(v, json!({ "a": {} }));
pub fn is_array(&self) -> bool
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Returns true if the Value
is an Array. Returns false otherwise.
For any Value on which is_array
returns true, as_array
and
as_array_mut
are guaranteed to return the vector representing the
array.
let obj = json!({ "a": ["an", "array"], "b": { "an": "object" } }); assert!(obj["a"].is_array()); // an object, not an array assert!(!obj["b"].is_array());
pub fn as_array(&self) -> Option<&Vec<Value>>
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If the Value
is an Array, returns the associated vector. Returns None
otherwise.
let v = json!({ "a": ["an", "array"], "b": { "an": "object" } }); // The length of `["an", "array"]` is 2 elements. assert_eq!(v["a"].as_array().unwrap().len(), 2); // The object `{"an": "object"}` is not an array. assert_eq!(v["b"].as_array(), None);
pub fn as_array_mut(&mut self) -> Option<&mut Vec<Value>>
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If the Value
is an Array, returns the associated mutable vector.
Returns None otherwise.
let mut v = json!({ "a": ["an", "array"] }); v["a"].as_array_mut().unwrap().clear(); assert_eq!(v, json!({ "a": [] }));
pub fn is_string(&self) -> bool
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Returns true if the Value
is a String. Returns false otherwise.
For any Value on which is_string
returns true, as_str
is guaranteed
to return the string slice.
let v = json!({ "a": "some string", "b": false }); assert!(v["a"].is_string()); // The boolean `false` is not a string. assert!(!v["b"].is_string());
pub fn as_str(&self) -> Option<&str>
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If the Value
is a String, returns the associated str. Returns None
otherwise.
let v = json!({ "a": "some string", "b": false }); assert_eq!(v["a"].as_str(), Some("some string")); // The boolean `false` is not a string. assert_eq!(v["b"].as_str(), None); // JSON values are printed in JSON representation, so strings are in quotes. // // The value is: "some string" println!("The value is: {}", v["a"]); // Rust strings are printed without quotes. // // The value is: some string println!("The value is: {}", v["a"].as_str().unwrap());
pub fn is_number(&self) -> bool
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Returns true if the Value
is a Number. Returns false otherwise.
let v = json!({ "a": 1, "b": "2" }); assert!(v["a"].is_number()); // The string `"2"` is a string, not a number. assert!(!v["b"].is_number());
pub fn is_i64(&self) -> bool
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Returns true if the Value
is an integer between i64::MIN
and
i64::MAX
.
For any Value on which is_i64
returns true, as_i64
is guaranteed to
return the integer value.
let big = i64::max_value() as u64 + 10; let v = json!({ "a": 64, "b": big, "c": 256.0 }); assert!(v["a"].is_i64()); // Greater than i64::MAX. assert!(!v["b"].is_i64()); // Numbers with a decimal point are not considered integers. assert!(!v["c"].is_i64());
pub fn is_u64(&self) -> bool
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Returns true if the Value
is an integer between zero and u64::MAX
.
For any Value on which is_u64
returns true, as_u64
is guaranteed to
return the integer value.
let v = json!({ "a": 64, "b": -64, "c": 256.0 }); assert!(v["a"].is_u64()); // Negative integer. assert!(!v["b"].is_u64()); // Numbers with a decimal point are not considered integers. assert!(!v["c"].is_u64());
pub fn is_f64(&self) -> bool
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Returns true if the Value
is a number that can be represented by f64.
For any Value on which is_f64
returns true, as_f64
is guaranteed to
return the floating point value.
Currently this function returns true if and only if both is_i64
and
is_u64
return false but this is not a guarantee in the future.
let v = json!({ "a": 256.0, "b": 64, "c": -64 }); assert!(v["a"].is_f64()); // Integers. assert!(!v["b"].is_f64()); assert!(!v["c"].is_f64());
pub fn as_i64(&self) -> Option<i64>
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If the Value
is an integer, represent it as i64 if possible. Returns
None otherwise.
let big = i64::max_value() as u64 + 10; let v = json!({ "a": 64, "b": big, "c": 256.0 }); assert_eq!(v["a"].as_i64(), Some(64)); assert_eq!(v["b"].as_i64(), None); assert_eq!(v["c"].as_i64(), None);
pub fn as_u64(&self) -> Option<u64>
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If the Value
is an integer, represent it as u64 if possible. Returns
None otherwise.
let v = json!({ "a": 64, "b": -64, "c": 256.0 }); assert_eq!(v["a"].as_u64(), Some(64)); assert_eq!(v["b"].as_u64(), None); assert_eq!(v["c"].as_u64(), None);
pub fn as_f64(&self) -> Option<f64>
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If the Value
is a number, represent it as f64 if possible. Returns
None otherwise.
let v = json!({ "a": 256.0, "b": 64, "c": -64 }); assert_eq!(v["a"].as_f64(), Some(256.0)); assert_eq!(v["b"].as_f64(), Some(64.0)); assert_eq!(v["c"].as_f64(), Some(-64.0));
pub fn is_boolean(&self) -> bool
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Returns true if the Value
is a Boolean. Returns false otherwise.
For any Value on which is_boolean
returns true, as_bool
is
guaranteed to return the boolean value.
let v = json!({ "a": false, "b": "false" }); assert!(v["a"].is_boolean()); // The string `"false"` is a string, not a boolean. assert!(!v["b"].is_boolean());
pub fn as_bool(&self) -> Option<bool>
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If the Value
is a Boolean, returns the associated bool. Returns None
otherwise.
let v = json!({ "a": false, "b": "false" }); assert_eq!(v["a"].as_bool(), Some(false)); // The string `"false"` is a string, not a boolean. assert_eq!(v["b"].as_bool(), None);
pub fn is_null(&self) -> bool
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Returns true if the Value
is a Null. Returns false otherwise.
For any Value on which is_null
returns true, as_null
is guaranteed
to return Some(())
.
let v = json!({ "a": null, "b": false }); assert!(v["a"].is_null()); // The boolean `false` is not null. assert!(!v["b"].is_null());
pub fn as_null(&self) -> Option<()>
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If the Value
is a Null, returns (). Returns None otherwise.
let v = json!({ "a": null, "b": false }); assert_eq!(v["a"].as_null(), Some(())); // The boolean `false` is not null. assert_eq!(v["b"].as_null(), None);
pub fn pointer(&self, pointer: &str) -> Option<&Value>
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Looks up a value by a JSON Pointer.
JSON Pointer defines a string syntax for identifying a specific value within a JavaScript Object Notation (JSON) document.
A Pointer is a Unicode string with the reference tokens separated by /
.
Inside tokens /
is replaced by ~1
and ~
is replaced by ~0
. The
addressed value is returned and if there is no such value None
is
returned.
For more information read RFC6901.
Examples
let data = json!({ "x": { "y": ["z", "zz"] } }); assert_eq!(data.pointer("/x/y/1").unwrap(), &json!("zz")); assert_eq!(data.pointer("/a/b/c"), None);
pub fn pointer_mut(&mut self, pointer: &str) -> Option<&mut Value>
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Looks up a value by a JSON Pointer and returns a mutable reference to that value.
JSON Pointer defines a string syntax for identifying a specific value within a JavaScript Object Notation (JSON) document.
A Pointer is a Unicode string with the reference tokens separated by /
.
Inside tokens /
is replaced by ~1
and ~
is replaced by ~0
. The
addressed value is returned and if there is no such value None
is
returned.
For more information read RFC6901.
Example of Use
use serde_json::Value; fn main() { let s = r#"{"x": 1.0, "y": 2.0}"#; let mut value: Value = serde_json::from_str(s).unwrap(); // Check value using read-only pointer assert_eq!(value.pointer("/x"), Some(&1.0.into())); // Change value with direct assignment *value.pointer_mut("/x").unwrap() = 1.5.into(); // Check that new value was written assert_eq!(value.pointer("/x"), Some(&1.5.into())); // Or change the value only if it exists value.pointer_mut("/x").map(|v| *v = 1.5.into()); // "Steal" ownership of a value. Can replace with any valid Value. let old_x = value.pointer_mut("/x").map(Value::take).unwrap(); assert_eq!(old_x, 1.5); assert_eq!(value.pointer("/x").unwrap(), &Value::Null); }
pub fn take(&mut self) -> Value
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Takes the value out of the Value
, leaving a Null
in its place.
let mut v = json!({ "x": "y" }); assert_eq!(v["x"].take(), json!("y")); assert_eq!(v, json!({ "x": null }));
Trait Implementations
impl Clone for Value
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impl Debug for Value
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impl Default for Value
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impl<'de> Deserialize<'de> for Value
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impl<'de> Deserializer<'de> for Value
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impl<'de> Deserializer<'de> for &'de Value
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impl Display for Value
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impl Eq for Value
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impl<'a, T: Clone + Into<Value>> From<&'a [T]> for Value
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impl<'a> From<&'a str> for Value
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impl From<()> for Value
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impl<'a> From<Cow<'a, str>> for Value
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impl From<Map<String, Value>> for Value
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impl From<Number> for Value
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impl From<String> for Value
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impl<T: Into<Value>> From<Vec<T, Global>> for Value
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impl From<bool> for Value
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impl From<f32> for Value
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impl From<f64> for Value
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impl From<i16> for Value
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impl From<i32> for Value
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impl From<i64> for Value
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impl From<i8> for Value
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impl From<isize> for Value
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impl From<u16> for Value
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impl From<u32> for Value
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impl From<u64> for Value
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impl From<u8> for Value
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impl From<usize> for Value
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impl<K: Into<String>, V: Into<Value>> FromIterator<(K, V)> for Value
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impl<T: Into<Value>> FromIterator<T> for Value
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impl FromStr for Value
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impl<I> Index<I> for Value where
I: Index,
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I: Index,
impl<I> IndexMut<I> for Value where
I: Index,
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I: Index,
impl<'de> IntoDeserializer<'de, Error> for Value
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impl<'a> PartialEq<&'a str> for Value
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impl PartialEq<String> for Value
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impl PartialEq<Value> for Value
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impl PartialEq<Value> for str
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impl PartialEq<Value> for u16
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impl PartialEq<Value> for u32
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impl PartialEq<Value> for u64
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impl PartialEq<Value> for usize
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impl PartialEq<Value> for f32
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impl PartialEq<Value> for f64
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impl PartialEq<Value> for bool
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impl<'a> PartialEq<Value> for &'a str
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impl PartialEq<Value> for String
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impl PartialEq<Value> for i8
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impl PartialEq<Value> for i16
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impl PartialEq<Value> for i32
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impl PartialEq<Value> for i64
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impl PartialEq<Value> for isize
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impl PartialEq<Value> for u8
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impl PartialEq<bool> for Value
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impl<'a> PartialEq<bool> for &'a Value
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impl<'a> PartialEq<bool> for &'a mut Value
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impl PartialEq<f32> for Value
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impl<'a> PartialEq<f32> for &'a Value
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impl<'a> PartialEq<f32> for &'a mut Value
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impl PartialEq<f64> for Value
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impl<'a> PartialEq<f64> for &'a Value
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impl<'a> PartialEq<f64> for &'a mut Value
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impl PartialEq<i16> for Value
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impl<'a> PartialEq<i16> for &'a Value
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impl<'a> PartialEq<i16> for &'a mut Value
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impl PartialEq<i32> for Value
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impl<'a> PartialEq<i32> for &'a Value
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impl<'a> PartialEq<i32> for &'a mut Value
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impl PartialEq<i64> for Value
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impl<'a> PartialEq<i64> for &'a Value
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impl<'a> PartialEq<i64> for &'a mut Value
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impl PartialEq<i8> for Value
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impl<'a> PartialEq<i8> for &'a Value
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impl<'a> PartialEq<i8> for &'a mut Value
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impl PartialEq<isize> for Value
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impl<'a> PartialEq<isize> for &'a Value
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impl<'a> PartialEq<isize> for &'a mut Value
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impl PartialEq<str> for Value
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impl PartialEq<u16> for Value
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impl<'a> PartialEq<u16> for &'a Value
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impl<'a> PartialEq<u16> for &'a mut Value
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impl PartialEq<u32> for Value
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impl<'a> PartialEq<u32> for &'a Value
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impl<'a> PartialEq<u32> for &'a mut Value
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impl PartialEq<u64> for Value
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impl<'a> PartialEq<u64> for &'a Value
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impl<'a> PartialEq<u64> for &'a mut Value
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impl PartialEq<u8> for Value
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impl<'a> PartialEq<u8> for &'a Value
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impl<'a> PartialEq<u8> for &'a mut Value
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impl PartialEq<usize> for Value
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impl<'a> PartialEq<usize> for &'a Value
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impl<'a> PartialEq<usize> for &'a mut Value
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impl Serialize for Value
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impl StructuralEq for Value
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impl StructuralPartialEq for Value
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Auto Trait Implementations
impl RefUnwindSafe for Value
impl Send for Value
impl Sync for Value
impl Unpin for Value
impl UnwindSafe for Value
Blanket Implementations
impl<T> Any for T where
T: 'static + ?Sized,
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T: 'static + ?Sized,
impl<T> Borrow<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> BorrowMut<T> for T where
T: ?Sized,
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T: ?Sized,
impl<T> DeserializeOwned for T where
T: for<'de> Deserialize<'de>,
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T: for<'de> Deserialize<'de>,
impl<T> From<T> for T
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impl<T, U> Into<U> for T where
U: From<T>,
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U: From<T>,
impl<T> ToOwned for T where
T: Clone,
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T: Clone,
impl<T> ToString for T where
T: Display + ?Sized,
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T: Display + ?Sized,
impl<T, U> TryFrom<U> for T where
U: Into<T>,
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U: Into<T>,
impl<T, U> TryInto<U> for T where
U: TryFrom<T>,
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U: TryFrom<T>,