V语言 泛型(Generics)

struct Repo <T> {
	db DB
}
 
fn new_repo<T>(db DB) Repo<T> {
	return Repo<T>{db: db}
}
 
// This is a generic function. V will generate it for every type it's used with. 
fn (r Repo<T>) find_by_id(id int) T? {
	table_name := T.name // in this example getting the name of the type gives us the table name 
	return r.db.query_one<T>('select * from $table_name where id = ?', id)
}
 
fn main() {
	db := new_db()
	users_repo := new_repo<User>(db)
	posts_repo := new_repo<Post>(db)
	user := users_repo.find_by_id(1)?
	post := posts_repo.find_by_id(1)?
} 

The initial version of V had generics because arrays and maps were built with them. Later I figured out a way to implement these data structures without generics. This simplified code greatly.

Since I no longer needed them, they were moved to a branch, because maintaining generics is tough. Generics will not be available when the language is released in June, but they should be back by July.

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