Constructors and destructors

Sometimes you want to initialize the field of a struct or execute some action right after creating an instance of it. Spice enables you doing that, by supporting constructors. To clean up a struct instance, destructors can be used.

Constructors¶

Whenever you create a struct instance like this, Spice will automatically call the ctor method of this struct:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
13
14
15

type ExampleStruct struct {
    string message
    bool showMessage
}

p ExampleStruct.ctor() {
    this.message = "Hello world!";
    showMessage = false;
}

f<int> main() {
    // Note the parentheses instead of the braces of a normal struct instantiation
    ExampleStruct es = ExampleStruct();
    // Do something with 'es' ...
}

Constructors can also have arguments to pass some information from the caller to the constructor of the struct:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11

// Struct definition ...

p ExampleStruct.ctor(string msg = "Hello World!") {
    this.message = msg;
    showMessage = false;
}

f<int> main() {
    ExampleStruct es = ExampleStruct("Hi fellow programmers!");
    // Do something with 'es' ...
}

The ctor method can also be called manually like calling other methods.

Destructors¶

You have the option to create a destructor by providing a dtor method on a struct. It does not allow any arguments and has no return type, since it is a procedure. Destructors can be especially useful for de-allocating objects in heap memory, that were allocated via malloc(). Whenever a struct variable goes out of scope somewhere in the program, the compiler searches for a destructor and calls it if available.

Here is an example for a custom destructor:

 1
 2
 3
 4
 5
 6
 7
 8
 9
10

// Declarations of the generic type T as well as malloc() and free() ...

type ExampleStruct<T> struct {
    string message
    T* messageObject
}

p ExampleStruct.dtor() {
    free(this.messageObject);
}