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> The name `json2` was chosen to avoid any unwanted potential conflicts with the
> existing codegen tailored for the main `json` module which is powered by CJSON.
`x.json2` is an experimental JSON parser written from scratch on V.
## Usage
```v oksyntax
import x.json2
import net.http
fn main() {
// Decoding
resp := http.get('https://example.com') ?
// raw decode
raw_person := json2.raw_decode(resp.text) ?
// Casting `Any` type / Navigating
person := raw_person.as_map()
name := person['name'].str() // Bob
age := person['age'].int() // 19
pi := person['pi'].f64() // 3.14....
// Constructing an `Any` type
mut me := map[string]json2.Any{}
me['name'] = 'Bob'
me['age'] = 18
mut arr := []json2.Any{}
arr << 'rock'
arr << 'papers'
arr << json2.null
arr << 12
me['interests'] = arr
mut pets := map[string]json2.Any{}
pets['Sam'] = 'Maltese Shitzu'
me['pets'] = pets
// Stringify to JSON
println(me.str())
//{
// "name":"Bob",
// "age":18,
// "interests":["rock","papers","scissors",null,12],
// "pets":{"Sam":"Maltese"}
//}
// Encode a struct/type to JSON
encoded_json := json2.encode<Person>(person2)
}
```
## Using `decode<T>` and `encode<T>`
> Codegen for this feature is still WIP.
> You need to manually define the methods before using the module to structs.
In order to use the `decode<T>` and `encode<T>` function, you need to explicitly define
two methods: `from_json` and `to_json`. `from_json` accepts a `json2.Any` argument
and inside of it you need to map the fields you're going to put into the type.
As for `to_json` method, you just need to map the values into `json2.Any`
and turn it into a string.
```v ignore
struct Person {
mut:
name string
age int = 20
pets []string
}
fn (mut p Person) from_json(f json2.Any) {
obj := f.as_map()
for k, v in obj {
match k {
'name' { p.name = v.str() }
'age' { p.age = v.int() }
'pets' { p.pets = v.arr().map(it.str()) }
else {}
}
}
}
fn (p Person) to_json() string {
mut obj := map[string]json2.Any
obj['name'] = p.name
obj['age'] = p.age
obj['pets'] = p.pets
return obj.str()
}
fn main() {
resp := os.read_file('./person.json')?
person := json2.decode<Person>(resp)?
println(person) // Person{name: 'Bob', age: 28, pets: ['Floof']}
person_json := json2.encode<Person>(person)
println(person_json) // {"name": "Bob", "age": 28, "pets": ["Floof"]}
}
```
## Using struct tags
`x.json2` can access and use the struct field tags similar to the
`json` module by using the comp-time `$for` for structs.
```v ignore
fn (mut p Person) from_json(f json2.Any) {
mp := an.as_map()
mut js_field_name := ''
$for field in Person.fields {
js_field_name = field.name
for attr in field.attrs {
if attr.starts_with('json:') {
js_field_name = attr.all_after('json:').trim_left(' ')
break
}
}
match field.name {
'name' { p.name = mp[js_field_name].str() }
'age' { u.age = mp[js_field_name].int() }
'pets' { u.pets = mp[js_field_name].arr().map(it.str()) }
else {}
}
}
}
```
### Null Values
`x.json2` has a separate `null` type for differentiating an undefined value and a null value.
To verify that the field you're accessing is a `null`, use `<typ> is json2.Null`.
```v ignore
fn (mut p Person) from_json(f json2.Any) {
obj := f.as_map()
if obj['age'] is json2.Null {
// use a default value
p.age = 10
}
}
```
### Custom field names
Aside from using struct tags, you can also just simply cast the base field into a map (`as_map()`)
and access the field you wish to put into the struct/type.
```v ignore
fn (mut p Person) from_json(f json2.Any) {
obj := f.as_map()
p.name = obj['nickname'].str()
}
```
```v oksyntax
fn (mut p Person) to_json() string {
obj := f.as_map()
obj['nickname'] = p.name
return obj.str()
}
```
### Undefined Values
Getting undefined values has the same behavior as regular V types.
If you're casting a base field into `map[string]json2.Any` and fetch an undefined entry/value,
it simply returns empty. As for the `[]json2.Any`, it returns an index error.
## Casting a value to an incompatible type
`x.json2` provides methods for turning `Any` types into usable types.
The following list shows the possible outputs when casting a value to an incompatible type.
1. Casting non-array values as array (`arr()`) will return an array with the value as the content.
2. Casting non-map values as map (`as_map()`) will return a map with the value as the content.
3. Casting non-string values to string (`str()`) will return the
JSON string representation of the value.
4. Casting non-numeric values to int/float (`int()`/`i64()`/`f32()`/`f64()`) will return zero.
|
