trait的构造顺序:
- 首先调用超类构造器
- 特质构造器在超类构造器之后,类构造器之前执行
- 特质从左向右被构造
- 每个特质当中,父特质先被构造
- 如果多个特质共有一个父特质,而那个父特质已经被构造,则不会被再次构造
- 所有特质构造完毕,子类被构造
class Account { println("Account constructor") } trait Logged { println("Logged constructor") def log(msg: String){ println("Logged")} } trait LongLogger extends Logged{ println("LongLogger constructor") override def log(msg: String){ println("LongLogger") super.log(msg) } } trait ShortLogger extends Logged{ println("ShortLogger constructor") override def log(msg: String){ println("ShortLogger") super.log(msg) } } trait ConsoleLogger extends Logged { println("ConsoleLogger constructor") override def log(msg: String){ println("ConsoleLogger") super.log(msg) } } trait DetailedLogger{ println("DetailedLogger constructor") def log2(msg: String){ println("DetailedLogger") } } class SavingsAccount extends Account with LongLogger with ShortLogger with ConsoleLogger { println("SavingsAccount constructor") log("funds") } new SavingsAccount() with DetailedLogger
运行结果:
Account constructor
Logged constructor
LongLogger constructor
ShortLogger constructor
ConsoleLogger constructor
SavingsAccount constructor
ConsoleLogger
ShortLogger
LongLogger
Logged
DetailedLogger constructor