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v/examples/compiletime/reflection.v

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V

// An example deserializer implementation
struct User {
name string
age int
}
fn main() {
data := 'name=Alice\nage=18'
user := decode[User](data)
println(user)
}
fn decode[T](data string) T {
mut result := T{}
// compile-time `for` loop
// T.fields gives an array of a field metadata type
$for field in T.fields {
$if field.typ is string {
// $(string_expr) produces an identifier
result.$(field.name) = get_string(data, field.name)
} $else $if field.typ is int {
result.$(field.name) = get_int(data, field.name)
}
}
return result
}
fn get_string(data string, field_name string) string {
for line in data.split_into_lines() {
key_val := line.split('=')
if key_val[0] == field_name {
return key_val[1]
}
}
return ''
}
fn get_int(data string, field string) int {
return get_string(data, field).int()
}
// `decode<User>` generates:
// fn decode_User(data string) User {
// mut result := User{}
// result.name = get_string(data, 'name')
// result.age = get_int(data, 'age')
// return result
// }