Question

简介

目标：在Scala方法中使用（多个）setter。

测试

test("testCity") {
  val numberSequences = new NumberSequences()
  numberSequences.test("utrecht")
  assert("utrecht" === numberSequences.city)
}

代码

var _city: String = null 

def city_=(_city:String) = this._city = _city  
def city = this._city

def test(s: String)  : String = {
  city_=(s)
}

输出

错误表示存在类型匹配，这在测试中与numberSequences.city_=("utrecht")一样奇怪。

> test
[info] Compiling 1 Scala source to C:\path\to\developme
nt\scalaNumberSequences\target\scala-2.10\classes...
[error] C:\path\to\development\scalaNumberSequences\src
\main\scala\com\utrecht\numbersequences\NumberSequences.scala:86: type mismatch;

[error]  found   : Unit
[error]  required: String
[error]     city_=(s)
[error]           ^
[error] one error found
[error] (compile:compile) Compilation failed
[error] Total time: 1 s, completed Aug 10, 2014 8:53:37 PM

Answer 1

def test(s: String)  : String = {
  city_=(s)
}

在这里设置var city_的变量，但是你的方法签名说它应该返回一个String，函数的返回类型来自最后一行而赋值没有返回类型，要么返回一些字符串最后：

def test(s: String): String = {
  city_=(s)
  s
}

或者使它成为类似于setter的方法并返回单位：

def test(s: String): Unit = {
  city_=(s)
}

在Scala方法中使用Setter

1 个答案: