How do I iterate over a JSON list? (rust) - json

Question

I am loafing a gltf asset (basically a big json file). I want to iterate over one of the fields, i.e. I am doing this:
let data = fs::read_to_string("Assets/werewolf_animated.gltf").expect("Unable to read file");
let json: serde_json::Value =
serde_json::from_str(&data).expect("JSON was not well-formatted");
for skin in json["skins"].into()
{
println!("{:?}", skin["inverseBindMatrices"]);
}
But apparently rust cannot infer the type, I get:
println!("{:?}", skin["inverseBindMatrices"]);
| ^^^^ cannot infer type
How can I iterate over every entry in the skins json array?
For what is worth this is what the specific field looks like in the json file:
"skins" : [
{
"inverseBindMatrices" : 5,
"joints" : [
64,
53,
52,
51,
2,
],
"name" : "Armature"
}
],

Answer 1

Value is an enum of all of the possible types of JSON values, so you have to handle the non-array cases as well (null values, booleans, numbers, strings, and objects). The helper Value::as_array() method returns an Option which is None in the non-array cases:
if let Some(skins) = json["skins"].as_array() {
for skin in skins {
// ...
}
}
In this case, this is pretty much equivalent to:
if let serde_json::Value::Array(skins) = json["skins"] {
for skin in skins {
// ...
}
}
If you want to signal an error via Result when this value isn't an array, you can combine Value::as_array() with Option::ok_or(). Here is an example, which assumes the presence of a custom error enum DataParseError:
for skin in json["skins"].as_array().ok_or(DataParseError::SkinsNotAnArray)? {
// ...
}