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Scala | Trait Mixins
  • Last Updated : 15 Apr, 2019

We can extend several number of scala traits with a class or an abstract class that is known to be trait Mixins. It is worth knowing that only traits or blend of traits and class or blend of traits and abstract class can be extended by us. It is even compulsory here to maintain the sequence of trait Mixins or else the compiler will throw an error.
Note:

  1. The Mixins traits are utilized in composing a class.
  2. A Class can hardly have a single super-class, but it can have numerous trait Mixins. The super-class and the trait Mixins might have identical super-types.

Now, lets see some examples.

  • Extending abstract class with trait
    Example :




    // Scala program of trait Mixins
      
    // Trait structure
    trait Display
      
        def Display() 
      
    // An abstract class structure
    abstract class Show
        def Show() 
      
    // Extending abstract class with
    // trait
    class CS extends Show with Display
    {
          
        // Defining abstract class
        // method
        def Display()
        {     
            // Displays output
            println("GeeksforGeeks"
        
          
        // Defining trait method
        def Show()
        {                                     
            // Displays output 
            println("CS_portal"
        
    }
      
    // Creating object
    object GfG
        // Main method
        def main(args:Array[String])
        
              
            // Creating object of class CS
            val x = new CS() 
              
            // Calling abstract method
            x.Display() 
              
            // Calling trait method
            x.Show() 
        
    Output:
    GeeksforGeeks
    CS_portal
    

    Here, the correct order of Mixins is that, we need to extend any class or abstract class first and then extend any trait by using a keyword with.

  • Extending abstract class without trait
    Example :




    // Scala program of trait Mixins
      
    // Trait structure
    trait Text
        def txt() 
    }
      
    // An abstract class structure
    abstract class LowerCase
        def lowerCase() 
      
    // Extending abstract class 
    // without trait
    class Myclass extends LowerCase
    {
          
        // Defining abstract class
        // method
        def lowerCase()
        
            val y = "GEEKSFORGEEKS"
              
            // Displays output
            println(y.toLowerCase()) 
        
          
        // Defining trait method
        def txt()
        {                                     
          
            // Displays output 
            println("I like GeeksforGeeks"
        
      
    // Creating object
    object GfG
        // Main method
        def main(args:Array[String])
        
              
            // Creating object of 'Myclass'
            // with trait 'Text'
            val x = new Myclass() with Text
              
            // Calling abstract method
            x.lowerCase() 
              
            // Calling trait method
            x.txt() 
        
    Output:
    geeksforgeeks
    I like GeeksforGeeks
    

    Thus, from this example we can say that the trait can even be extended while creating object.
    Note: If we extend a trait first and then the abstract class then the compiler will throw an error, as that is not the correct order of trait Mixins.




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