Learn notes from scratch (day 39)-constructor overloading

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Constructors can also be overloaded as a special method.

Swift The constructors can be multiple, and their argument lists and return values can be different, and these constructors form overloads.

The sample code is as follows:

class rectangle {        var width: double     var height: double        init (Width:  double, height: double)  {        self.width    = width        self.height  = height     }        init (W width: Double,H  height: double) {          self.width    = width        self.height  = height     }        init (length: double)  {             self.width   = length          self.height  = length    }     init ()  {          self.width   = 640.0         self.height  = 940.0    }  } var rectc1 =rectangle (width: 320.0, height: 480.0)   print ("Rectangle : \ (rectc1.width)  x\ (rectc1.height) ")  var rectc2 = rectangle (W: 320.0, H:  480.0)            print ("Rectangle: \ (rectc2.width)   X\ (rectc2.height) ")  var rectc3 =rectangle (length: 500.0)                  print ("Rectangle 3:\ (rectc3.width)  x\ ( Rectc3.height)  var rectc4 = rectangle ()               &Nbsp;          print ("Rectangle 4:\ (rectc4.width)  x\ ( Rectc4.height) ")

Constructor Proxy

to reduce code duplication among multiple constructors, you can define a constructor by calling other constructors to complete the partial construction of the instance, called Constructor Proxy . Constructor proxies are used differently in structs and classes, and the constructor proxies in structs are introduced first.

The example in the previous section is modified as follows:

struct rectangle {     var width: double     Var height: double        init (width: Double,  height: double)  {        self.width   =  width        self.height  = height     }        init (w width: double,h height:  Double) {          self.width   = width         self.height  = height    }         init (length: double)  {                     //called the Self.init statement          self.init (w: length, h: length)     }      init ()  {                               // Called the Self.init statement         self.init (width: 640.0, height:  940.0)     } } var rectc1 =rectangle (width: 320.0, height:  480.0)   print ("Rectangle: \ (rectc1.width)  x\ (rectc1.height)")  var rectc2 =  Rectangle (w: 320.0, h: 480.0)             Print ("Rectangle: \ (rectc2.width)  x\ (rectc2.height)")  var rectc3 =rectangle (length: 500.0)                 print ("Rectangular 3:\ ( Rectc3.width)  x\ (Rectc3.height)  var rectc4 = rectangle ()                          print ("Rectangular 4:\ ( Rectc4.width)  x \ (rectc4.height) ")

will be Rectangle declared as struct type, which also has 4 overload of the constructor function.

This is done in the same type Self.init statement to invoke other constructors of the current type, other constructors are called constructor proxies.

class constructor Horizontal Proxy

Because classes have inheritance relationships, class constructor proxies are more complex and are divided into horizontal and upward proxies.

• Horizontal Agent similar to struct type constructor proxies, which occur inside the same class, such constructors are called Convenient constructor function (convenience initializers).

• up Proxy In the case of inheritance, the parent class constructor is called to initialize the storage properties of the parent class during the subclass construction, which is called the Specifying Constructors (designated initializers).

The above example is modified as follows:

class rectangle {     var width: double     Var height: double        init (width: Double,  height: double) {            self.width    = width        self.height  = height     }        init (W width: Double,H  height: double) {               self.width   = width        self.height   = height    }        convenience  init (length: double)  {                      self.init (w: length, h: length)     }      convenience init ()  {                                Self.init (width: 640.0, height: 940.0)     } } VAR RECTC1  =rectangle (width: 320.0, height: 480.0)   print ("Rectangle: \ (rectc1.width)  x\ ( Rectc1.height)  var rectc2 = rectangle (w: 320.0, h: 480.0)             print ("Rectangle: \ (rectc2.width)  x\ (rectc2.height)")  var rectc3 =rectangle (length: 500.0)                  print ("Rectangle 3:\ (rectc3.width)  x\ (rectc3.height)")  var  rectc4 = rectangle () &Nbsp;                        print ("Rectangle 4:\ (rectc4.width)  x\ (rectc4.height)")

will be Rectangle declared as classes, which also have 4 overload of the constructor function.

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Learn notes from scratch (day 39)-constructor overloading