cannot assign 1 values to 2 variables [simple error handling]

[Ângelo Chida]

Hi, I'm new in Golang but I'm PHP StackDev since 10 years ago

I'm following this tutorial https://golang.org/doc/articles/wiki/ on how to build a web app, but I'm stuck on some error and can't find anywhere a solution. Please help

Take a look at the image

My go version is 1.9

*sorry for poor english, it is not my native language

[Ian Lance Taylor]

You are trying to assign the result of loadPage to two variables, but loadPage only returns one result.

In the "here is OK" section you are assigning the result of ioutil.ReadFile to two variables.  That is OK because ioutil.ReadFile returns two results.  You can see the definition of ioutil.ReadFile at https://golang.org/src/io/ioutil/ioutil.go#L45 .

Ian

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[Elias Naur]

Just to expand on Ian's reply: you seem to want to have loadPage return any errors, similar to what ReaedFile does. If so, you need to declare loadPage to return two values, like so:

func loadPage(title string) (*Page, error)

And return a nil *Page and the error if ReadFile fails:

body, err := ioutil.ReadFile(filename)

if err != nil {

    return nil, err

}

The same goes for the sucess path:

return &Page{Title: title, Body: body}, nil

HTH,

 - elias

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[Mhd Shulhan]

On 18/09/17 10:00, Ângelo Chida wrote:
> Hi, I'm new in Golang but I'm PHP StackDev since 10 years ago
> I'm following this tutorial https://golang.org/doc/articles/wiki/ on
> how to build a web app, but I'm stuck on some error and can't find
> anywhere a solution.

If you read down into "Data Structure" section, you will find the
explanation for those function.

> Functions can return multiple values. The standard library function
|io.ReadFile|returns |[]byte|and |error|. In |loadPage|, error isn't
being handled yet; the "blank identifier" represented by the underscore
(|_|) symbol is used to throw away the error return value (in essence,
assigning the value to nothing).
>
> But what happens if |ReadFile|encounters an error? For example, the
file might not exist. We should not ignore such errors. Let's modify the
function to return |*Page|and |error|.
>
> func loadPage(title string) (*Page, error) {
>    filename := title + ".txt"

>    body, err := ioutil.ReadFile(filename)
>    if err != nil {
>        return nil, err
>    }

[Ângelo Chida]

I understand now, thank you all