Structs in Lua

Structs in Lua

Lua’s tables serve a similar purpose to structs in other languages. They’re used for grouping data together to form records.

This person table has name and age fields.

person = {name = "", age = 0}

In Lua, you can create new instances of the table like this:

function newPerson(name)
    local p = {name = name, age = 42}
    return p
end

Here’s the full example translated to Lua, including the main function:

-- Define the person table
person = {name = "", age = 0}

-- Function to create a new person
function newPerson(name)
    local p = {name = name, age = 42}
    return p
end

-- Main function demonstrating how to use the person table
function main()
    -- Create new person instances
    print({name = "Bob", age = 20})
    print({name = "Alice", age = 30})
    print({name = "Fred"})

    -- Create a person and output a pointer-like behavior
    ann = {name = "Ann", age = 40}
    print(ann)

    -- Using the constructor function
    jon = newPerson("Jon")
    print(jon)

    -- Accessing fields
    local s = {name = "Sean", age = 50}
    print(s.name)

    local sp = s
    print(sp.age)

    -- Updating struct fields
    sp.age = 51
    print(sp.age)

    -- Using an anonymous struct (table)
    local dog = {
        name = "Rex",
        isGood = true
    }
    print(dog)
end

main()

Output explanation:

The code initializes and uses Lua tables to simulate struct-like behavior.
Lua tables dynamically grow and shrink in size and can hold any Lua value, which can be seen as an advantage over fixed-structured formats in other languages.
Lua uses the print function to output values. When printing tables, a custom function can be written to format the output as Lua’s native print function does not format tables by default.

Now, let’s run the main function and see the output.

$ lua structs.lua

Output:

table: name = Bob, age = 20
table: name = Alice, age = 30
table: name = Fred, age = 0
table: name = Ann, age = 40
table: name = Jon, age = 42
Sean
50
51
table: name = Rex, isGood = true

After understanding how Lua handles structs using tables, we can now delve deeper into other data handling techniques in Lua.

Strings and Runes in Lua

Methods in Lua

Learn X By Example

Title here

Structs in Lua