Kotlin Infix函数的使用方法

假设你有一副扑克牌，你是这样定义的

//花形
enum class Suit {
  HEARTS,
  SPADES,
  CLUBS,
  DIAMONDS
}

//数字
enum class Rank {
  TWO, THREE, FOUR, FIVE,
  SIX, SEVEN, EIGHT, NINE,
  TEN, JACK, QUEEN, KING, ACE 
}
data class Card(val rank: Rank, val suit: Suit)

你可以这样生成一张牌：

val card = Card(Rank.QUEEN, Suit.HEARTS)

如果你想把两个属性链接起来：

enum class Rank {
  TWO, THREE, FOUR, FIVE,
  SIX, SEVEN, EIGHT, NINE,
  TEN, JACK, QUEEN, KING, ACE;
  fun of(suit: Suit) = Card(this, suit)
}

你可以这样生成一张牌：

val card = Rank.QUEEN.of(Suit.HEARTS)

但是，如果你用了infix的话：

enum class Rank {
  TWO, THREE, FOUR, FIVE,
  SIX, SEVEN, EIGHT, NINE,
  TEN, JACK, QUEEN, KING, ACE;
 
  infix fun of(suit: Suit) = Card(this, suit)
}

你可以这样生成一张牌：

val card = QUEEN of HEARTS

代码出自：
https://medium.com/makingtuenti/infix-functions-in-kotlin-2db3d3142dd2