| <!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Source of the Rust file `/root/.cargo/registry/src/github.com-1ecc6299db9ec823/serde_json-1.0.96/src/value/index.rs`."><meta name="keywords" content="rust, rustlang, rust-lang"><title>index.rs - source</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Regular.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../FiraSans-Medium.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Regular.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceSerif4-Bold.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../../../SourceCodePro-Semibold.ttf.woff2"><link rel="stylesheet" href="../../../normalize.css"><link rel="stylesheet" href="../../../rustdoc.css" id="mainThemeStyle"><link rel="stylesheet" href="../../../ayu.css" disabled><link rel="stylesheet" href="../../../dark.css" disabled><link rel="stylesheet" href="../../../light.css" id="themeStyle"><script id="default-settings" ></script><script src="../../../storage.js"></script><script defer src="../../../source-script.js"></script><script defer src="../../../source-files.js"></script><script defer src="../../../main.js"></script><noscript><link rel="stylesheet" href="../../../noscript.css"></noscript><link rel="alternate icon" type="image/png" href="../../../favicon-16x16.png"><link rel="alternate icon" type="image/png" href="../../../favicon-32x32.png"><link rel="icon" type="image/svg+xml" href="../../../favicon.svg"></head><body class="rustdoc source"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="sidebar"><a class="sidebar-logo" href="../../../serde_json/index.html"><div class="logo-container"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></div></a></nav><main><div class="width-limiter"><nav class="sub"><a class="sub-logo-container" href="../../../serde_json/index.html"><img class="rust-logo" src="../../../rust-logo.svg" alt="logo"></a><form class="search-form"><div class="search-container"><span></span><input class="search-input" name="search" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" title="help" tabindex="-1"><a href="../../../help.html">?</a></div><div id="settings-menu" tabindex="-1"><a href="../../../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../../../wheel.svg"></a></div></div></form></nav><section id="main-content" class="content"><div class="example-wrap"><pre class="src-line-numbers"><span id="1">1</span> |
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| </pre><pre class="rust"><code><span class="kw">use </span><span class="kw">super</span>::Value; |
| <span class="kw">use </span><span class="kw">crate</span>::map::Map; |
| <span class="kw">use </span>alloc::borrow::ToOwned; |
| <span class="kw">use </span>alloc::string::String; |
| <span class="kw">use </span>core::fmt::{<span class="self">self</span>, Display}; |
| <span class="kw">use </span>core::ops; |
| |
| <span class="doccomment">/// A type that can be used to index into a `serde_json::Value`. |
| /// |
| /// The [`get`] and [`get_mut`] methods of `Value` accept any type that |
| /// implements `Index`, as does the [square-bracket indexing operator]. This |
| /// trait is implemented for strings which are used as the index into a JSON |
| /// map, and for `usize` which is used as the index into a JSON array. |
| /// |
| /// [`get`]: ../enum.Value.html#method.get |
| /// [`get_mut`]: ../enum.Value.html#method.get_mut |
| /// [square-bracket indexing operator]: ../enum.Value.html#impl-Index%3CI%3E |
| /// |
| /// This trait is sealed and cannot be implemented for types outside of |
| /// `serde_json`. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # use serde_json::json; |
| /// # |
| /// let data = json!({ "inner": [1, 2, 3] }); |
| /// |
| /// // Data is a JSON map so it can be indexed with a string. |
| /// let inner = &data["inner"]; |
| /// |
| /// // Inner is a JSON array so it can be indexed with an integer. |
| /// let first = &inner[0]; |
| /// |
| /// assert_eq!(first, 1); |
| /// ``` |
| </span><span class="kw">pub trait </span>Index: private::Sealed { |
| <span class="doccomment">/// Return None if the key is not already in the array or object. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">fn </span>index_into<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span>Value>; |
| |
| <span class="doccomment">/// Return None if the key is not already in the array or object. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">fn </span>index_into_mut<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value>; |
| |
| <span class="doccomment">/// Panic if array index out of bounds. If key is not already in the object, |
| /// insert it with a value of null. Panic if Value is a type that cannot be |
| /// indexed into, except if Value is null then it can be treated as an empty |
| /// object. |
| </span><span class="attribute">#[doc(hidden)] |
| </span><span class="kw">fn </span>index_or_insert<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value; |
| } |
| |
| <span class="kw">impl </span>Index <span class="kw">for </span>usize { |
| <span class="kw">fn </span>index_into<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span>Value> { |
| <span class="kw">match </span>v { |
| Value::Array(vec) => vec.get(<span class="kw-2">*</span><span class="self">self</span>), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="kw">fn </span>index_into_mut<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value> { |
| <span class="kw">match </span>v { |
| Value::Array(vec) => vec.get_mut(<span class="kw-2">*</span><span class="self">self</span>), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="kw">fn </span>index_or_insert<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value { |
| <span class="kw">match </span>v { |
| Value::Array(vec) => { |
| <span class="kw">let </span>len = vec.len(); |
| vec.get_mut(<span class="kw-2">*</span><span class="self">self</span>).unwrap_or_else(|| { |
| <span class="macro">panic!</span>( |
| <span class="string">"cannot access index {} of JSON array of length {}"</span>, |
| <span class="self">self</span>, len |
| ) |
| }) |
| } |
| <span class="kw">_ </span>=> <span class="macro">panic!</span>(<span class="string">"cannot access index {} of JSON {}"</span>, <span class="self">self</span>, Type(v)), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Index <span class="kw">for </span>str { |
| <span class="kw">fn </span>index_into<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span>Value> { |
| <span class="kw">match </span>v { |
| Value::Object(map) => map.get(<span class="self">self</span>), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="kw">fn </span>index_into_mut<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value> { |
| <span class="kw">match </span>v { |
| Value::Object(map) => map.get_mut(<span class="self">self</span>), |
| <span class="kw">_ </span>=> <span class="prelude-val">None</span>, |
| } |
| } |
| <span class="kw">fn </span>index_or_insert<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value { |
| <span class="kw">if let </span>Value::Null = v { |
| <span class="kw-2">*</span>v = Value::Object(Map::new()); |
| } |
| <span class="kw">match </span>v { |
| Value::Object(map) => map.entry(<span class="self">self</span>.to_owned()).or_insert(Value::Null), |
| <span class="kw">_ </span>=> <span class="macro">panic!</span>(<span class="string">"cannot access key {:?} in JSON {}"</span>, <span class="self">self</span>, Type(v)), |
| } |
| } |
| } |
| |
| <span class="kw">impl </span>Index <span class="kw">for </span>String { |
| <span class="kw">fn </span>index_into<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span>Value> { |
| <span class="self">self</span>[..].index_into(v) |
| } |
| <span class="kw">fn </span>index_into_mut<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value> { |
| <span class="self">self</span>[..].index_into_mut(v) |
| } |
| <span class="kw">fn </span>index_or_insert<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value { |
| <span class="self">self</span>[..].index_or_insert(v) |
| } |
| } |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>, T> Index <span class="kw">for </span><span class="kw-2">&</span><span class="lifetime">'a </span>T |
| <span class="kw">where |
| </span>T: <span class="question-mark">?</span>Sized + Index, |
| { |
| <span class="kw">fn </span>index_into<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span>Value> { |
| (<span class="kw-2">**</span><span class="self">self</span>).index_into(v) |
| } |
| <span class="kw">fn </span>index_into_mut<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value> { |
| (<span class="kw-2">**</span><span class="self">self</span>).index_into_mut(v) |
| } |
| <span class="kw">fn </span>index_or_insert<<span class="lifetime">'v</span>>(<span class="kw-2">&</span><span class="self">self</span>, v: <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value) -> <span class="kw-2">&</span><span class="lifetime">'v </span><span class="kw-2">mut </span>Value { |
| (<span class="kw-2">**</span><span class="self">self</span>).index_or_insert(v) |
| } |
| } |
| |
| <span class="comment">// Prevent users from implementing the Index trait. |
| </span><span class="kw">mod </span>private { |
| <span class="kw">pub trait </span>Sealed {} |
| <span class="kw">impl </span>Sealed <span class="kw">for </span>usize {} |
| <span class="kw">impl </span>Sealed <span class="kw">for </span>str {} |
| <span class="kw">impl </span>Sealed <span class="kw">for </span>alloc::string::String {} |
| <span class="kw">impl</span><<span class="lifetime">'a</span>, T> Sealed <span class="kw">for </span><span class="kw-2">&</span><span class="lifetime">'a </span>T <span class="kw">where </span>T: <span class="question-mark">?</span>Sized + Sealed {} |
| } |
| |
| <span class="doccomment">/// Used in panic messages. |
| </span><span class="kw">struct </span>Type<<span class="lifetime">'a</span>>(<span class="kw-2">&</span><span class="lifetime">'a </span>Value); |
| |
| <span class="kw">impl</span><<span class="lifetime">'a</span>> Display <span class="kw">for </span>Type<<span class="lifetime">'a</span>> { |
| <span class="kw">fn </span>fmt(<span class="kw-2">&</span><span class="self">self</span>, formatter: <span class="kw-2">&mut </span>fmt::Formatter) -> fmt::Result { |
| <span class="kw">match </span><span class="kw-2">*</span><span class="self">self</span>.<span class="number">0 </span>{ |
| Value::Null => formatter.write_str(<span class="string">"null"</span>), |
| Value::Bool(<span class="kw">_</span>) => formatter.write_str(<span class="string">"boolean"</span>), |
| Value::Number(<span class="kw">_</span>) => formatter.write_str(<span class="string">"number"</span>), |
| Value::String(<span class="kw">_</span>) => formatter.write_str(<span class="string">"string"</span>), |
| Value::Array(<span class="kw">_</span>) => formatter.write_str(<span class="string">"array"</span>), |
| Value::Object(<span class="kw">_</span>) => formatter.write_str(<span class="string">"object"</span>), |
| } |
| } |
| } |
| |
| <span class="comment">// The usual semantics of Index is to panic on invalid indexing. |
| // |
| // That said, the usual semantics are for things like Vec and BTreeMap which |
| // have different use cases than Value. If you are working with a Vec, you know |
| // that you are working with a Vec and you can get the len of the Vec and make |
| // sure your indices are within bounds. The Value use cases are more |
| // loosey-goosey. You got some JSON from an endpoint and you want to pull values |
| // out of it. Outside of this Index impl, you already have the option of using |
| // value.as_array() and working with the Vec directly, or matching on |
| // Value::Array and getting the Vec directly. The Index impl means you can skip |
| // that and index directly into the thing using a concise syntax. You don't have |
| // to check the type, you don't have to check the len, it is all about what you |
| // expect the Value to look like. |
| // |
| // Basically the use cases that would be well served by panicking here are |
| // better served by using one of the other approaches: get and get_mut, |
| // as_array, or match. The value of this impl is that it adds a way of working |
| // with Value that is not well served by the existing approaches: concise and |
| // careless and sometimes that is exactly what you want. |
| </span><span class="kw">impl</span><I> ops::Index<I> <span class="kw">for </span>Value |
| <span class="kw">where |
| </span>I: Index, |
| { |
| <span class="kw">type </span>Output = Value; |
| |
| <span class="doccomment">/// Index into a `serde_json::Value` using the syntax `value[0]` or |
| /// `value["k"]`. |
| /// |
| /// Returns `Value::Null` 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 `Value::Null` if the given key does not exist |
| /// in the map or the given index is not within the bounds of the array. |
| /// |
| /// For retrieving deeply nested values, you should have a look at the |
| /// `Value::pointer` method. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # use serde_json::json; |
| /// # |
| /// let data = json!({ |
| /// "x": { |
| /// "y": ["z", "zz"] |
| /// } |
| /// }); |
| /// |
| /// assert_eq!(data["x"]["y"], json!(["z", "zz"])); |
| /// assert_eq!(data["x"]["y"][0], json!("z")); |
| /// |
| /// assert_eq!(data["a"], json!(null)); // returns null for undefined values |
| /// assert_eq!(data["a"]["b"], json!(null)); // does not panic |
| /// ``` |
| </span><span class="kw">fn </span>index(<span class="kw-2">&</span><span class="self">self</span>, index: I) -> <span class="kw-2">&</span>Value { |
| <span class="kw">static </span>NULL: Value = Value::Null; |
| index.index_into(<span class="self">self</span>).unwrap_or(<span class="kw-2">&</span>NULL) |
| } |
| } |
| |
| <span class="kw">impl</span><I> ops::IndexMut<I> <span class="kw">for </span>Value |
| <span class="kw">where |
| </span>I: Index, |
| { |
| <span class="doccomment">/// Write into a `serde_json::Value` using the syntax `value[0] = ...` or |
| /// `value["k"] = ...`. |
| /// |
| /// If the index is a number, the value must be an array of length bigger |
| /// than the index. Indexing into a value that is not an array or an array |
| /// that is too small will panic. |
| /// |
| /// If the index is a string, the value must be an object or null which is |
| /// treated like an empty object. If the key is not already present in the |
| /// object, it will be inserted with a value of null. Indexing into a value |
| /// that is neither an object nor null will panic. |
| /// |
| /// # Examples |
| /// |
| /// ``` |
| /// # use serde_json::json; |
| /// # |
| /// let mut data = json!({ "x": 0 }); |
| /// |
| /// // replace an existing key |
| /// data["x"] = json!(1); |
| /// |
| /// // insert a new key |
| /// data["y"] = json!([false, false, false]); |
| /// |
| /// // replace an array value |
| /// data["y"][0] = json!(true); |
| /// |
| /// // inserted a deeply nested key |
| /// data["a"]["b"]["c"]["d"] = json!(true); |
| /// |
| /// println!("{}", data); |
| /// ``` |
| </span><span class="kw">fn </span>index_mut(<span class="kw-2">&mut </span><span class="self">self</span>, index: I) -> <span class="kw-2">&mut </span>Value { |
| index.index_or_insert(<span class="self">self</span>) |
| } |
| } |
| </code></pre></div> |
| </section></div></main><div id="rustdoc-vars" data-root-path="../../../" data-current-crate="serde_json" data-themes="ayu,dark,light" data-resource-suffix="" data-rustdoc-version="1.66.0-nightly (5c8bff74b 2022-10-21)" ></div></body></html> |
