Learning Golang, Day 10 – Type Assertions, Type Switches, and Stringers.

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I enjoyed the session, as it, on the whole, made sense. Type https://go.dev/tour/methods/15[assertions] and https://go.dev/tour/methods/16[switches] were pretty self-explanatory, and something that I look forward to using. The same goes for https://go.dev/tour/methods/17[Stringers], which remind me a lot of PHP’s https://www.php.net/manual/en/language.oop5.magic.php#object.tostring[magic __toString function].

Because of that comparison, they’re what I want to focus on for just a bit. From what I understand, to implement a Stringer, all you have to do is to add a method to a Type in Go named String that returns a string.

In PHP, if a class implements the __toString method, which returns a string, then the object can be used as a string. Here’s an example to demonstrate what I’m talking about.

[source,php]

firstName, $this->lastName); } } $user = new User("Matthew", "Setter"); echo $user; ---- In this example, when the code is run, the string "Matthew Setter" will be printed to the terminal. However, when I started working through https://go.dev/tour/methods/18[the Stringers exercise], things started to come undone. You can see the sample code below. [source,go] ---- package main import "fmt" type IPAddr [4]byte // TODO: Add a "String() string" method to IPAddr. func main() { hosts := map[string]IPAddr{ "loopback": {127, 0, 0, 1}, "googleDNS": {8, 8, 8, 8}, } for name, ip := range hosts { fmt.Printf("%v: %v\n", name, ip) } } ---- I looked at the example and thought that I'd just have to create a `String()` method with a pointer receiver to the `IPAddr` type, that: . Converted the byte array to a string or array of strings . Joined the string array together into a single string, where each element was separated by a dot/period, as in the example below . Returned the string [source,go] ---- func (ipa IPAddr) String() string { var output []string for _, v := range ipa { output = append(output, string(v)) } return strings.Join(output, ".") } ---- That didn't work, as it converted the byte values to strings, not a string representation of the byte's value I don't know if I explained that correctly. What I mean is that, for example, it converted 127 to the `DEL` char, and 0 to the `NULL` char, instead of converting 127 to "127" and 0 to "0", etc. I hope that makes sense. I kept playing further but didn't really make a lot of progress. To try and get "unstuck", I asked a question in the newbies channel in gophers.slack.com and am currently having a discussion about it. I hope to work through this and, in the next session, be able to solve the exercise. What's more, I am happy for having gotten stuck, as it's helped me to start to appreciate a wider array of types that I'd been used to for quite some time now. **See you, link:/learning-golang/day-11[next time]!**