README.md

Functions and consumers with default parameters factory

Use this module if you need function or consumer with default parameter such as it's possible in some other programming languages.

Uses Type Tools to resolve variadic params

Uses jUnit for autotests

---

Purpose

If you need function or consumer with some default parameter such as in other programming languages, for example:

Python:

def a(a = 1, b = 2):
        ...

C++:

int a(int a = 1, int b = 2) 
{ 
    ...
}

PHP:

function a(int $a = 1, int $b = 2) { 
    ... 
}

a(1);
a(1, 2)

JAVA [ DefargFunc ]:

var a = registerConsumer((var b, var c) -> { /* ... */ }, 1, 2);
a.apply(1);
a.apply(1, 2);

---

Installation

Install from Maven Repository

<dependency>
  <groupId>com.github.hadasbro</groupId>
  <artifactId>defargfunctions</artifactId>
  <version>1.0.2</version>
</dependency>

Usage

You can use FuntionFactory to register function or consumer as below.

1. Simple example (Java 11)

   var showSum = registerConsumer((var a, var b) ->  {System.out.println(a + b);}, 1, 2);
   
   showSum.apply(); // 3
   showSum.apply(11); // 13
   showSum.apply(11,12); // 23

2. Consumer with 1 parameter and 1 default value

   Consumer1DefaultParams1<Integer> doSomething = registerConsumer(
   
           // consumer
           System.out::println,
   
           //default param 1
           150
   );
   
   doSomething.apply(); // 150
   doSomething.apply(250); // 250

3. Consumer with 2 parameters and 1 default value

   Consumer2DefaultParams1<Integer, String> doSomethingElse = registerConsumer(
   
       // consumer
       (Integer a, String str) -> {
   
           // consumer body
           System.out.println(a + " - " + str);
   
       },
   
       // mark param 1 as mandatory
       NO_DEFAULT,
   
       //default value for param 2
       "default string"
   );
   
   doSomethingElse.apply(1); // 1 - default string
   doSomethingElse.apply(250, "something"); // 250 - something

4. Consumer with 4 parameter and 2 default values

   Consumer4DefaultParams2<Integer, Integer, String, Character> myConsumer = registerConsumer(
   
       // consumer
       (Integer a, Integer b, String c, Character e) -> System.out.println(
               a + " -> " + b + "  ->  " + c + "  -> " + e
       ),
   
       // param 1 marked as mandatory
       NO_DEFAULT,
   
       // param 2 marked as mandatory
       NO_DEFAULT,
   
       // default value for param 3
       "default string",
   
       // default value for param 4
       'x'
   
   );
   
   // consumer call results:
   
   myConsumer.apply(2, 3, "test", 'a');
   // result: 2 -> 3  ->  test  -> a
   
   myConsumer.apply(2, 3, "test2");
   // result: 2 -> 3  ->  test  -> a
   
   myConsumer.apply(2, 3);
   // result: 2 -> 3  ->  default string  -> x

5. JAVA 11 consumer example

   Consumer2DefaultParams2<Integer, String> doSomethingNew = registerConsumer(
   
           // consumer
           (var a, var str) -> {
   
               // consumer body
               System.out.println(a + " - " + str);
   
           },
   
           // default value param 1
           150,
   
           // default value param 2
           "default string b"
   );
   
   doSomethingNew.apply(); // 150 - default string b
   doSomethingNew.apply(12); // 12 - default string b
   doSomethingNew.apply(13, "test string"); // 13 - test string

6. Consumer as lambda function in class

   class Test{
   
       Consumer2DefaultParams2<Integer, String> consumer = registerConsumer(
   
               // consumer
               (var a, var str) -> {
   
                   // consumer body
                   System.out.println(a + " - " + str);
   
               },
   
               // default value for param 2
               14,
   
               // default value for param 2
               "default string b"
       );
   
       public Test(){
           consumer.apply(); // 14 - default string b
           consumer.apply(12); // 12 - default string b
           consumer.apply(15, "abc"); // 15 - abc
       }
   
   }

7. Simple function (Java 11 style)

   /*
       function with 2 optional params
    */
   var multiply = registerFunction(
           (var a, var b) -> a * b,2, 3
   );
   
   Integer result1 = multiply.apply(); // 6
   Integer result2 = multiply.apply(7); // 21
   Integer result3 = multiply.apply(7, 4); // 28

8. Other function examples

   Function with 2 optional params.

   Function2DefaultParams2<String, Integer, Integer> func = registerFunction(
       (Integer a, Integer b) -> a + "," + b, 1, 2
   );
   
   String result1 = func.apply(); // 1,2
   String result2 = func.apply(22); // 22,2
   String result3 = func.apply(22, 33); // 22,33

   Function with 2 params but only 1 is optional

   Function2DefaultParams1<String, Integer, Integer> func2 = registerFunction(
       (Integer a, Integer b) -> a + "," + b, NO_DEFAULT, 2
   );
   
   String result5 = func2.apply(1); //1,2
   String result6 = func2.apply(11, 22); // 11,22

9. Function registered in class (Java 11 style)

   class Test{
   
       Function2DefaultParams2<Integer, Integer, Integer> sum = registerFunction(
               (var a, var b) -> a + b, 1, 2
       );
   
       public Test(){
           int mySum = sum.apply(100,200); // 300
       }
   
   }

---

Type hinting

Type hinting should suggest parameter types normally in all popular IDEs. Also if you specify e.g. consumer with 4 parameters and 2 dafeults, then IDE should suggest function/consumer parameters (all possible signatures) corectly as below.

---

Future, Todo

After bugfix in JDK [ JDK-8027181 ], default parameters will be provided via annotations as below.

(var a, @def(object) var bee, @def("def string") var ster, @def(123) var number) -> { /* body */ }

Authors

• Slawomir Hadas - author - Github