mirror of
https://github.com/chubin/cheat.sheets
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80 lines
1.6 KiB
Plaintext
80 lines
1.6 KiB
Plaintext
// constructor params - private
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class C(x: R) // same as
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class C(private val x: R)
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var c = new C(4)
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// constructor params - public
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class C(val x: R)
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var c = new C(4)
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c.x
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class C(var x: R) {
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// constructor is class body
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assert(x > 0, "positive please")
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//
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// declare a public member
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var y = x
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//
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// declare a gettable but not settable member
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val readonly = 5
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//
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// declare a private member
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private var secret = 1
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//
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// alternative constructor
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def this = this(42)
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}
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// anonymous class
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new{ ... }
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// define an abstract class. (non-createable)
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abstract class D { ... }
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// define an inherited class.
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class C extends D { ... }
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class D(var x: R)
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// inheritance and constructor params. (wishlist: automatically pass-up params
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// by default)
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class C(x: R) extends D(x)
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// define a singleton. (module-like)
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object O extends D { ... }
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// traits.
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trait T { ... }
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// interfaces-with-implementation. no constructor params. mixin-able:
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//
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// http://docs.scala-lang.org/tutorials/tour/mixin-class-composition.html
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//
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class C extends T { ... }
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class C extends D with T { ... }
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// multiple traits.
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trait T1; trait T2
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class C extends T1 with T2
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class C extends D with T1 with T2
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// must declare method overrides.
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class C extends D { override def f = ...}
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// create object.
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new java.io.File("f")
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new List[Int] // BAD type error: abstract type
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List(1,2,3) // GOOD instead, convention: callable factory shadowing the type
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// class literal.
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classOf[String]
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// type check (runtime)
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x.isInstanceOf[String]
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// type cast (runtime)
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x.asInstanceOf[String]
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// ascription (compile time)
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x: String
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