在子類里,我們可以通過重載父類方法來改變實體的行為.

ruby>classHuman

|defidentify

|print"I'maperson.\n"

|end

|deftrain_toll(age)

|ifage<12

|print"Reducedfare.\n";

|else

|print"Normalfare.\n";

|end

|end

|end

nil

ruby>Human.new.identify

I'maperson.

nil

ruby>classStudent1

|defidentify

|print"I'mastudent.\n"

|end

|end

nil

ruby>Student1.new.identify

I'mastudent.

nil

如果我們只是想增強父類的identify方法而不是完全地替代它,就可以用super.

ruby>classStudent2

|defidentify

|super

|print"I'mastudenttoo.\n"

|end

|end

nil

ruby>Student2.new.identify

I'mahuman.

I'mastudenttoo.

nil

super也可以讓我們向原有的方法傳遞參數.這里有時會有兩種類型的人...

ruby>classDishonest

|deftrain_toll(age)

|super(11)#wewantacheapfare.

|end

|end

nil

ruby>Dishonest.new.train_toll(25)

Reducedfare.

nil

ruby>classHonest

|deftrain_toll(age)

|super(age)#passtheargumentweweregiven

|end

|end

nil

ruby>Honest.new.train_toll(25)

Normalfare.

nil