A minimal json crate conforming to https://www.ecma-international.org/publications/files/ECMA-ST/ECMA-404.pdf .
In order to create a valid (i.e. generally accepted) json you should always start with: ```rust use json_minimal::*;
let mut json = Json::new();
// which is equivalent to
let mut json = Json::JSON(Vec::new());
// ...
```
To add an object, simply do this: ```rust // ... let greeting = Json::OBJECT { name: String::from("Greeting"),
value: Box::new(
Json::STRING( String::from("Hello, world!") )
)
}
;
json.add(greeting);
// ...
or alternatively:
rust
// ...
json.add(
Json::OBJECT {
name: String::from("Greeting"),
value: Box::new(
Json::STRING( String::from("Hello, world!") )
)
}
);
// ...
```
As you can see, whilst the crate is minimal (in my opinion) it may not be the quickest to work with. This becomes clearer when adding an array to an object: ```rust // ...
let mut days_in_the_week =
Json::OBJECT {
name: String::from("Days of the week"),
value: Box::new(
Json::JSON(Vec::new())
)
}
;
let mut days = Json::ARRAY(Vec::new());
days
.add(
Json::STRING( String::from("Monday") )
)
.add(
Json::STRING( String::from("Tuesday") )
)
.add(
Json::STRING( String::from("Wednesday") )
)
.add(
Json::STRING( String::from("Thursday") )
)
.add(
Json::STRING( String::from("Friday") )
)
.add(
Json::STRING( String::from("Saturday") )
)
.add(
Json::STRING( String::from("Sunday") )
)
;
days_in_the_week
.add(
Json::OBJECT {
name: String::from("Total number of days"),
value: Box::new(
Json::NUMBER(7.0) // Accepts `f64`
)
}
)
.add(
Json::OBJECT {
name: String::from("They are called"),
value: Box::new(
days
)
}
)
;
json.add(days_in_the_week);
// ...
```
In conclusion: ```rust // ...
let mut conclusion =
Json::OBJECT {
name: String::from("Conclusion"),
value: Box::new(
Json::JSON(Vec::new())
)
}
;
conclusion
.add(
Json::OBJECT {
name: String::from("Minimal in my opinion"),
value: Box::new(
Json::BOOL(true)
)
}
)
.add(
Json::OBJECT {
name: String::from("How much I care about your opinion"),
value: Box::new(
Json::NULL
)
}
)
.add(
Json::OBJECT {
name: String::from("Comment"),
value: Box::new(
Json::STRING( String::from(";)") )
)
}
)
;
json.add(conclusion);
// ...
```
Calling:
rust
// ...
let resulting_json = json.print();
will result in a String containing:
{"Greeting":"Hello, world!","Days of the week":{"Total number of days":7,"They are called":["Monday","Tuesday","Wednesday","Thursday","Friday","Saturday","Sunday"]},"Conclusion":{"Minimal in my opinion":true,"How much I care about your opinion":null,"Comment":";)"}}
If you would like the json string in a different format you can easily make your own 'print' function.
Parsing a json value from bytes is even more minimal - at the cost of being more cumbersome. Let's see how we can parse the json we generated above: ```rust use json_minimal::*;
let json = match Json::parse(b"{\"Greeting\":\"Hello, world!\",\"Days of the week\":{\"Total number of days\":7,\"They are called\":[\"Monday\",\"Tuesday\",\"Wednesday\",\"Thursday\",\"Friday\",\"Saturday\",\"Sunday\"]},\"Conclusion\":{\"Minimal in my opinion\":true,\"How much I care about your opinion\":null,\"Comment\":\";)\"}}") {
Ok(json) => {
json
},
Err( (position,message) ) => {
panic!("`{}` at position `{}`!!!");
}
}
// ...
```
Let's first talk about what information is given for a parsing error. As you might expect it is minimal. position above is the position were everything went wrong and the message will be something like"Error parsing array." if, for example, a closing ] is missing somewhere. Continuing where we left off:
rust
// ...
match json.get("Greeting") {
Some(json) => {
match json {
Json::OBJECT { name: _, value } => {
match value.unbox() {
Json::STRING(val) => {
assert_eq!("Hello, world!",val);
},
json => {
panic!("Expected Json::STRING but found {:?}",json);
}
}
},
json => {
panic!("Expected Json::JSON but found {:?}!!!",json)
}
}
},
None => {
panic!("Couln't find Greeting. How rude!");
}
}
// ...
Unfortunately all of this was necessary because, even though we were able to confirm that "Greeting" exists, we had no way of knowing what it really is. It's not over:
``rust
// ...
match json.get("Days of the week") { // Hint: You can also usegetmut` to aid in editing/creating jsons...
Some(json) => {
match json {
Json::OBJECT { name: _, value } => {
match value.unbox() {
Json::JSON(values) => {
asserteq!(values.len(),2);
match &values[0] {
Json::OBJECT { name, value: _ } => {
assert_eq!("Total number of days",name);
},
json => {
panic!("Expected Json::OBJECT but found {:?}!!!",json);
}
}
match &values[1] {
Json::OBJECT { name, value: _ } => {
assert_eq!("They are called",name);
},
json => {
panic!("Expected Json::OBJECT but found {:?}!!!",json);
}
}
},
json => {
panic!("Expected Json::JSON but found {:?}!!!",json);
}
}
},
json => {
panic!("Expected Json::OBJECT but found {:?}!!!",json);
}
}
},
None => {
panic!("Days of the week not found!");
}
}
// You get the idea.
``
The functionJson::parse(...)` can also parse 'standalone values'. Example:
``rust
match Json::parse("\"What's up?\"") {
Ok(json) => {
match json {
Json::STRING(val) => {
assert_eq!("What's up?",val);
},
json => {
panic!("Expected Json::STRING but found {:?}!!!",json);
}
}
},
Err( (position,message) ) => {
panic!("{}at position{}`.");
}
}
// Another example:
match Json::parse("[1,2,3,\"four\"]") {
Ok(json) => {
match json {
Json::ARRAY(val) => {
assert_eq!(val.len(),4);
},
json => {
panic!("Expected Json::ARRAY but found {:?}!!!",json);
}
}
},
Err( (position,message) ) => {
panic!("`{}` at position `{}`.");
}
}
```
Lonami (github) has made improvements:
json_minimal can now parse non-ASCII strings and escape sequences. (I overlooked this, I admit.)A thousand thanks to Lonami !!!
json_minimal can now also parse 'pretty' json like this (as long as only \r, \n, \t and whitespace were used for formatting):
{
"Array": [ "Hello" , "World" , "!" ]
}
This should also have worked from the start but I did not include because it of my aversion to energy inefficiency (although it is, perhaps, unfounded).
Please let me know if something doesn't work. I can't promise i'll react immediately, though.