覆盖 toString 时如何使用条件语句

Question

I'm trying to override toString using conditional statements. But I'm getting an error that says there is a type mismatch. It is supposed to be in String type and right now it's in Any type. noGoals, Tied are functions that returns true or false.

override def toString = {
  if (this.noGoals)
    s"${this.home} vs. ${this.away} at ${this.location}: no goals"
  else if (this.Tied)
    s"${this.home} vs. ${this.away} at ${this.location}: tied"
}




    

Answer 1

The expression

if (conditionA) "aa"
else if (conditionB) "bb"

defaults to

if (conditionA) "aa"        
else if (conditionB) "bb"   
else ()                     // oops () types to Unit

where value () has Unit type, whilst values "aa" and "bb" have type String , and least upper bound of Unit and String is Any . Thus try providing default string to the last else branch like so

if (conditionA) "aa"
else if (conditionB) "bb"
else "default"