first.gno.md

first.gno

The first.gno realm declares variables, constants, and functions.

Realm Code

// first.gno

package first

import "gno.land/p/demo/avl"

var myVar = 1

const myConst = 10

var initlVar int

func init() {
	initlVar = 1000
}

func GetInitValue() int {
	return initlVar
}

func get() int {
	return myVar
}

func Get() int {
	return myVar
}

func Inc() int {
	myVar += 1
	return myVar
}

func IncByInput(inc int) int {
	myVar += inc
	return myVar
}

func Dec() {
	myVar -= 1
}

func ImpossibleInc() {
	myConst += 1
}

Let's break down the code by each segment.

var myVar = 1

const myConst = 10

var initlVar int

func init() {
	initlVar = 1000
}

func GetInitValue() int {
	return initlVar
}

The code block above displays the variable & constant declaration code (and 2 functions). The init() function is a pre-defined function that serves a similar purpose as that of the Golang (executed with priority upon initializing or importing a package).

As a result, once the code above is executed, the initlVar variable with only a declared data type, but without an initial value, is assigned with a value of 1000.

func get() int {
	return myVar
}

func Get() int {
	return myVar
}

func Inc() int {
	myVar += 1
	return myVar
}

func IncByInput(inc int) int {
	myVar += inc
	return myVar
}

func Dec() {
	myVar -= 1
}

func ImpossibleInc() {
	myConst += 1
}

The code block above displays the function declaration code.

The get() function and the Get() function are equivalent in functionality, except the capitalization of the latter, which serves to implement the previously discussed access control mechanism.

The Inc() function and the IncByInput() function are designed to increment the value of myVar. Note that the IncByInput function specifically obtains the number to be increased, as an argument, from the user.

The Dec() function decrements the value of myVar. However, as it does not possess a return value, an additional function must be used to verify the result.

The ImpossibleInc() function at the end results in an error as it attempts to modify the value of the constant.

Test Code

// first_test.gno

package first

import "testing"

func Test(t *testing.T) {
	// GetInitValue
	{
		got := GetInitValue()
		expected := 1000
		if got != expected {
			t.Fatalf("expected %v, got %v.", expected, got)
		}
	}

	// get
	{
		got := get()
		expected := 1
		if got != expected {
			t.Fatalf("expected %v, got %v.", expected, got)
		}
	}

	// Get
	{
		got := Get()
		expected := 1
		if got != expected {
			t.Fatalf("expected %v, got %v.", expected, got)
		}
	}

	// Inc
	{
		got := Inc()
		expected := 2
		if got != expected {
			t.Fatalf("expected %v, got %v.", expected, got)
		}
	}

	// IncByInput
	{
		got := IncByInput(777)
		expected := 779
		if got != expected {
			t.Fatalf("expected %v, got %v.", expected, got)
		}
	}

	// Dec
	{
		Dec() // can't assign return value since Dec() doesn't return anything
		got := Get()
		expected := 778
		if got != expected {
			t.Fatalf("expected %v, got %v.", expected, got)
		}
	}

	// ImpossibleInc()
	{
		// ImpossibleInc() // will panic, since myConst is const not var
	}
}