Non default constructor

When working with Julia, you may come across situations where you need to define a non-default constructor for your objects. A non-default constructor allows you to initialize the object with specific values when it is created. In this article, we will explore three different ways to solve the problem of defining a non-default constructor in Julia.

Option 1: Using a function to create the object

One way to solve the problem is by using a function to create the object with the desired values. Here’s an example:

struct MyObject
    value::Int64
end

function createObject(value::Int64)
    return MyObject(value)
end

obj = createObject(10)

In this option, we define a function called createObject that takes an Int64 value as input and returns a new instance of the MyObject struct with the specified value. This allows us to create objects with non-default values by simply calling the function with the desired value.

Option 2: Using a constructor method

Another way to solve the problem is by defining a constructor method within the struct definition. Here’s an example:

struct MyObject
    value::Int64

    function MyObject(value::Int64)
        new(value)
    end
end

obj = MyObject(10)

In this option, we define a constructor method with the same name as the struct. This method takes an Int64 value as input and uses the new keyword to create a new instance of the struct with the specified value. This allows us to create objects with non-default values by simply calling the constructor method with the desired value.

Option 3: Using default values and keyword arguments

A third way to solve the problem is by using default values and keyword arguments in the constructor. Here’s an example:

struct MyObject
    value::Int64

    function MyObject(value::Int64=0)
        new(value)
    end
end

obj = MyObject(value=10)

In this option, we define a constructor method with a default value of 0 for the value argument. This allows us to create objects with non-default values by specifying the desired value as a keyword argument when calling the constructor.

After exploring these three options, it is clear that the best option depends on the specific requirements of your code. Option 1 provides a separate function for object creation, which can be useful if you want to encapsulate the creation logic. Option 2 allows you to define the constructor method directly within the struct definition, making it more convenient for object creation. Option 3 provides flexibility by allowing default values and keyword arguments in the constructor. Consider your specific needs and choose the option that best suits your situation.