我对AboutExtractors.scala中的这个公案感到有点困惑。这段代码来自
https://bitbucket.org/dmarsh/scalakoansexercises/wiki/Home
koan("In this koan we use the unapply for pattern matching employee objects") {
class Employee(val firstName: String,
val middleName: Option[String],
val lastName: String)
object Employee {
//factory methods, extractors, apply
//Extractor: Create tokens that represent your object
def unapply(x: Employee) =
Some(x.lastName, x.middleName, x.firstName)
}
val singri = new Employee("Singri", None, "Keerthi")
val result = singri match {
case Employee("Singri", None, x) => "Yay, Singri %s! with no middle name!".format(x)
case Employee("Singri", Some(x), _) => "Yay, Singri with a middle name of %s".format(x)
case _ => "I don't care, going on break"
}
result should be("I don't care, going on break")
}
为什么不调用行case Employee("Singri", None, x) => "Yay, Singri %s! with no middle name!".format(x)？
在我看来Employee("Singri", None, "Keerthi")匹配Employee("Singri", None, x)。
答案 0 :(得分：0)
提取器（错误/不可取）更改类参数的顺序，将姓氏放在第一位。因此.atpcontent{
background-color:#bbb;
padding:10px 10px;
font-size:1em;
}
.atpcontent h2{
padding:0;
font-family:'raleway', arial, sans-serif;
font-size:1.5em;
font-weight:600;
color:#0e4373;
position: relative;
display: inline-block;
}
.atpcontent p{
padding:7px 0;
color:#0e4373;
font-size:1em;
font-family:'raleway',arial,sans-serif;}
.atpcontent img{
width:100%;
height:auto;}
.atpcontent a{
text-decoration:none;
font-weight:bold;
color:inherit;
transition:1s;}
.atpcontent a:hover{
color:#06C;
transition:1s;
}
.ajdrop{word-wrap:break-word;padding-bottom:10px;}
.ajdrop p{
padding:7px 0;
font-family:'raleway', arial, sans-serif;
color:#0e4373;
font-size:1em;}
/* dropdown arrow sections css */
.ajdrop h2{
background: url(assets/img/down.png) no-repeat 0 12px; /*comment this if you dont want arrows*/
padding:9px 0 0 20px;
font-family:'raleway', arial, sans-serif;
font-size:20px;
color:#0e4373;}
.ajdrop h2.close{background-image: url(assets/img/up.png);
}/*comment this if you dont want arrows*/
.aanswer{margin-left:35px;}
会匹配。