Retrieving an instance of an enum using a string

When working with Julia, there may be situations where you need to retrieve an instance of an enum using a string. This can be useful when you have a string representation of an enum value and you want to convert it back to the corresponding enum instance. In this article, we will explore three different ways to solve this problem.

Option 1: Using a Dictionary

One way to solve this problem is by using a dictionary. We can create a dictionary where the keys are the string representations of the enum values and the values are the corresponding enum instances. Here’s an example:

enum Color
    RED = "red"
    BLUE = "blue"
    GREEN = "green"
end

color_dict = Dict("red" => Color.RED, "blue" => Color.BLUE, "green" => Color.GREEN)

function get_enum_instance(color_str)
    return color_dict[color_str]
end

In this example, we define an enum called “Color” with three values: RED, BLUE, and GREEN. We then create a dictionary called “color_dict” where the keys are the string representations of the enum values and the values are the corresponding enum instances. The function “get_enum_instance” takes a string as input and returns the corresponding enum instance by looking it up in the dictionary.

Option 2: Using a Switch Statement

Another way to solve this problem is by using a switch statement. We can define a function that takes a string as input and uses a switch statement to return the corresponding enum instance. Here’s an example:

enum Color
    RED = "red"
    BLUE = "blue"
    GREEN = "green"
end

function get_enum_instance(color_str)
    case color_str
        "red" => return Color.RED
        "blue" => return Color.BLUE
        "green" => return Color.GREEN
    end
end

In this example, we define an enum called “Color” with three values: RED, BLUE, and GREEN. The function “get_enum_instance” takes a string as input and uses a switch statement to return the corresponding enum instance based on the input string.

Option 3: Using Metaprogramming

A more advanced way to solve this problem is by using metaprogramming. We can define a macro that takes a string as input and generates code to return the corresponding enum instance. Here’s an example:

enum Color
    RED = "red"
    BLUE = "blue"
    GREEN = "green"
end

macro get_enum_instance(color_str)
    esc(:(Color($(Symbol(color_str)))))
end

In this example, we define an enum called “Color” with three values: RED, BLUE, and GREEN. The macro “get_enum_instance” takes a string as input and generates code to return the corresponding enum instance by using the “Symbol” function to convert the input string to a symbol and then using the symbol to access the enum instance.

After exploring these three options, it is clear that using a dictionary is the most straightforward and readable solution. It allows for easy mapping between the string representations and the enum instances. The switch statement option is also a viable solution, but it can become cumbersome if there are many enum values. The metaprogramming option is the most advanced and flexible, but it may be overkill for simple cases like this.