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v/vlib/x/json2/README.md

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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.
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`x.json2` is an experimental JSON parser written from scratch on V.
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## Usage
#### encode[T]
```v
import x.json2
import time
struct Person {
mut:
name string
age ?int = 20
birthday time.Time
deathday ?time.Time
}
fn main() {
mut person := Person{
name: 'Bob'
birthday: time.now()
}
person_json := json2.encode[Person](person)
// person_json == {"name": "Bob", "age": 20, "birthday": "2022-03-11T13:54:25.000Z"}
}
```
#### decode[T]
```v
import x.json2
import time
struct Person {
mut:
name string
age ?int = 20
birthday time.Time
deathday ?time.Time
}
fn main() {
resp := '{"name": "Bob", "age": 20, "birthday": "${time.now()}"}'
person := json2.decode[Person](resp)!
/*
struct Person {
mut:
name "Bob"
age 20
birthday "2022-03-11 13:54:25"
}
*/
}
```
decode[T] is smart and can auto-convert the types of struct fields - this means
examples below will have the same result
```v ignore
json2.decode[Person]('{"name": "Bob", "age": 20, "birthday": "2022-03-11T13:54:25.000Z"}')!
json2.decode[Person]('{"name": "Bob", "age": 20, "birthday": "2022-03-11 13:54:25.000"}')!
json2.decode[Person]('{"name": "Bob", "age": "20", "birthday": 1647006865}')!
json2.decode[Person]('{"name": "Bob", "age": "20", "birthday": "1647006865"}}')!
```
#### raw decode
```v
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import x.json2
import net.http
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fn main() {
resp := http.get('https://reqres.in/api/products/1')!
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// This returns an Any type
raw_product := json2.raw_decode(resp.body)!
}
```
#### Casting `Any` type / Navigating
```v
import x.json2
import net.http
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fn main() {
resp := http.get('https://reqres.in/api/products/1')!
raw_product := json2.raw_decode(resp.body)!
product := raw_product.as_map()
data := product['data'] as map[string]json2.Any
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id := data['id'].int() // 1
name := data['name'].str() // cerulean
year := data['year'].int() // 2000
}
```
#### Constructing an `Any` type
```v
import x.json2
fn main() {
mut me := map[string]json2.Any{}
me['name'] = 'Bob'
me['age'] = 18
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mut arr := []json2.Any{}
arr << 'rock'
arr << 'papers'
arr << json2.null
arr << 12
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me['interests'] = arr
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mut pets := map[string]json2.Any{}
pets['Sam'] = 'Maltese Shitzu'
me['pets'] = pets
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// Stringify to JSON
println(me.str())
//{
// "name":"Bob",
// "age":18,
// "interests":["rock","papers","scissors",null,12],
// "pets":{"Sam":"Maltese"}
//}
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}
```
### 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`.
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```v ignore
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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
}
}
```
## 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.
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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.