To get all the matches by a discipline you can use Toornament::matches_by_discipline:

extern crate toornament;
use toornament::*;

fn main() {
    let toornament = Toornament::with_application("API_TOKEN",
                                                  "CLIENT_ID",
                                                  "CLIENT_SECRET").unwrap()
                                .timeout(5);

    // But let's look all the matches for wwe2k17 discipline
    let matches = toornament.matches_by_discipline(DisciplineId("wwe2k17".to_owned()),
                                                   MatchFilter::default());
}

matches will now contain a result with game matches for a wwe2k17 game discipline. Note, that this method accepts a filter as second parameter which can be used for filtering server's data. In the code above this filter is filled with default values.

If you want to do this via iter-like interface:

extern crate toornament;
use toornament::*;

fn main() {
    let toornament = Toornament::with_application("API_TOKEN",
                                                  "CLIENT_ID",
                                                  "CLIENT_SECRET").unwrap()
                                .timeout(5);

    let matches = toornament.disciplines_iter()
                            .with_id(DisciplineId("wwe2k17".to_owned()))
                            .matches()
                            .collect::<Matches>()
                            .unwrap();
}