hello.gno.md

hello.gno

Realm Code

// hello.gno

package hello

func Hello() string {
	return "Hello() called"
}

// func Render() string {
// 	return "Render() called"
// }

func Render(path string) string {
	return "Render(path string) called with\n# " + path
}

The hello realm is a simple code that returns a string by declaring the Hello() function and the Render() function.

Hello() can be called without an argument, butRender() must be called with a string-typed path parameter.

Note: Like Golang, function overloading is not supported in Gnolang.

Test Code

// hello_test.gno

package hello

import "testing"

func Test(t *testing.T) {
	{
		got := Hello()
		expected := "Hello() called"
		if got != expected {
			t.Fatalf("expected %q, got %q.", expected, got)
		}
	}

	{
		got := Render("")
		expected := "Render(path string) called with\n# "
		if got != expected {
			t.Fatalf("expected %q, got %q.", expected, got)
		}
	}

	{
		got := Render("n3wbie")
		expected := "Render(path string) called with\n# n3wbie"
		if got != expected {
			t.Fatalf("expected %q, got %q.", expected, got)
		}
	}
}

Let's test the code using gno test.

Then, let's publish the realm with gnokey addpkg.

Now, let's call the Render() function using all three methods.

1. Visiting the website

It is specified in the realm code that the Render() function must be invoked with the path string argument. However, the image provided illustrates that no additional characters have been concatenated to the end of the URL link.

The argument can be specified in the URL with the colon :.

2. The maketx call option using gnokey

The image above is an example of calling the function using maketx call.

It should be noted that when the (path string) argument is declared within the realm code, a failure to explicitly include an empty argument will result in an inability to successfully execute the function.

The drawback of using the maketx call method is that it consumes gas, as it creates an actual transaction on the network.

Functions that make changes to the state must have a subject for change, hence must create an actual transaction with options such as caller, gas-fee, and gas-wanted. In this case, however, as data retrieval without any state changes to the blockchain is out main objective, we can use the next method (query vm/qrender) to achieve the same result without spending any gas.

3. The query vm/qrender option using gnokey

This method involves seemingly fewer options compared to gnokey maketx call method. However, passing the argument can be quite confusing: the realm path that exposes the Render() function must be placed in the --data option, and the arguments in a new line (\n).

If we return to our realm code, we can see that the other function, Hello(), also doesn't cause any state changes to the blockchain.

Any other function besides Render() can be invoked with gnokey query vm/qeval.

In the image above, the first command uses the gnokey maketx call to call the function, and the second command uses the gnokey query vm/qeval.

It should be noted that there are distinct variations in the argument requirements between vm/qeval and vm/qrender. Specifically, when utilizing the vm/qeval method, it is mandatory to specify the function to be invoked and the corresponding parameters, immediately following a new line.

The Hello() function does not require any parameters, so the call can be executed by only specifying the function.

The Render() function can also be called with eval, but a distinct escaping (other than a single quotation ``) should be used when passing a string-typed argument as seen in the third method in the image above.