The understanding of object and class in Scala---The Apply method is the initialization method

1.class

Scala classes are a bit different from classes in C #, such as declaring a field that is not priavate decorated var age,scala compiler field helps us to produce a private field and 2 public method get and set, which is similar to C # 's simple properties; If you use the private adornment , its methods will also be private. This is the so-called unified access principle.

Too much detail, or the code in the comments.

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2. Class is the public level by default
4. Class person{
6. var age= //field must be initialized ()
8. def age=age //This is the method, no parameters can be omitted ()
10. Def incremen () {this.age+=1}
12. }
18. Class student{
20. var age= ///The underlying compiler automatically adds a public method of get and set to the private age, which can be understood as pseudo type
22. private[this] var gender="male" //private[this] only this class can use the
24. Private var name="Clow" //declares private, the underlying compiler automatically adds the get and set proprietary methods for the private name
26. //But you can define your own property methods
28. def getname=THIS.name
30. def setName (value:string) {This.name=value}
32. }
36. Use of constructors
38. Class Teacher {
40. var Age:int = _
42. var name:string = _ //Can be reserved
46. //Overloaded constructors are similar to the public Teacher () {} inside C #
48. def this (Age:int, name:string) {
50. This () //must be called once for the main constructor
52. This.age=age
54. This.name=name
56. }
58. }

Constructor details for class

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2. 1. The main constructor after the class name, the parameter is declared field, if the parameter is not used Var or Val declaration, it will be declared private field
4. 2. When instantiating a class, the statements in the class are executed: println ("person")
6. Class person (Name:string,var Age:int) {
8. println ("person")
12. Def show (): Unit = {
14. println ("show..") +name)
16. }
20. var gender:string=_
24. //Secondary constructor must call the main constructor, parameter cannot use Var
26. def this (Name:string,age:int, gender:string) {
28. This (name,age)
30. This.gender=gender
32. }
34. }

2.scala has no static modifier, but the member under object is static, and if there is a class with the same name, it acts as its companion class. In object, you can generally do some initialization for the associated class, such as the Val Array=array (PS: It uses the Apply method) that we often use

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1. Object dog{
2. private var age=0
3. def age={
4. age+=1
5. Age
6. }
7. }
9. Class dog{
10. var age1=dog.age //dog.age is a private field of object Dog. It reminds me of the friend class of C + + .
11. }

Use of 3.Apply

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2. Class applytest{
6. Val name="Clow";
8. def apply () {
10. println ("Class applytest--apply () ...");
12. }
16. }
20. The members under object are static by default
22. Object applytest{
24. def apply () = {
26. println ("Object applytest--apply () ...");
28. new Applytest ()
30. }
32. }
38. Object Basic4 {
42. def main (args:array[string]) {
44. //class name () called the Apply method under the corresponding object
46. var a1=applytest ()
48. println (A1.name)
50. //Object name (), call the Apply method of the corresponding class
52. A1 () //Output: Class applytest--apply () ...
54. }
56. }

Apply how to use it to implement a singleton mode

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2. Class Applytest private{ //Add private hidden constructor
4. Def SayHello () {
6. println ("Hello Jop")
8. }
10. }
14. Object applytest{
16. var instant:applytest=Null
18. def apply () ={
20. if (instant==null) instant=new applytest
22. Instant
26. }
28. }
32. Object Applydemo {
34. def main (args:array[string]) {
36. Val T=applytest ()
38. T.sayhello ()
40. }
42. }

The understanding of object and class in Scala---The Apply method is the initialization method