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How to use interfaces in Go (2012)

jordanorelli.com

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Re: How to use interfaces in Go (2012)

#21

Post by namelezz »

mseepgood wrote: post #18
ridiculous_fish wrote: post #14

When navigating unfamiliar Go codebases, it's hard to know which types fulfill an interface. Say you have a function that takes an Animal; how do you figure out what to call it with? Or to give a concrete example, say you want to do formatted output to stderr. How is one supposed to determine that os.Stderr is something that can be passed to fmt.Fprintf? Is there a better way than manually comparing method signatures…

Use the Go oracle with an "implements" query.

So beside familiarizing the language syntax, I need to be aware of a set of unofficial tools and plugins, which are likely going to change in the next couple months, to be able to read the code.

Re: How to use interfaces in Go (2012)

#22

Post by icholy »

laumars wrote: post #17
ThatGeoGuy wrote: post #9

Earlier quoted context omitted.

I don't think "terse" quite describes it. Python can be terse, as you can say: n = sum(x for x in my_sequence if x % 2 == 0) But the Go code listed above is not just plagued with a lot going on in "3 lines". I think there's something to be said about gratuitous operators, and a sort of beauty to letting the parser do more work than the programmer themselves. I don't use Go at all, but from the example above I can tel…

> I don't use Go at all, but from the example above I can tell it is a horribly grotesque language... If you don't us Go at all then you can't tell anything from a single 3 line example. It's like judging an entire Linux distro based solely on a couple of screenshots. What the he'll is going wrong with HN lately that I can't open a programming thread without superficial criticisms from someone who's never actually co…

Everyone's a PL expert.

Re: How to use interfaces in Go (2012)

#23

Post by icholy »

namelezz wrote: post #21
mseepgood wrote: post #18

Earlier quoted context omitted.

Use the Go oracle with an "implements" query.

So beside familiarizing the language syntax, I need to be aware of a set of unofficial tools and plugins, which are likely going to change in the next couple months, to be able to read the code.

It's an official tool. Also, most interfaces are very small (one to two methods) so it's pretty easy to figure out. I read/write a decent amount of Go every day and it's not often that I'm asking myself "what implements this interface?".

Re: How to use interfaces in Go (2012)

#24

Post by [deleted] »

jkubicek wrote: post #15
krat0sprakhar wrote: post #11

Earlier quoted context omitted.

Not sure I understand - what part of this is not easy to read? It's quite familiar to read and make sense to any programmer who's had experience with any of the C-like languages.

Is this sarcasm? That code snippet doesn't look like any C-like language that I'm familiar with.

[deleted]

Re: How to use interfaces in Go (2012)

#25

Post by [deleted] »

icholy wrote: post #22
laumars wrote: post #17

Earlier quoted context omitted.

> I don't use Go at all, but from the example above I can tell it is a horribly grotesque language... If you don't us Go at all then you can't tell anything from a single 3 line example. It's like judging an entire Linux distro based solely on a couple of screenshots. What the he'll is going wrong with HN lately that I can't open a programming thread without superficial criticisms from someone who's never actually co…

Everyone's a PL expert.

[deleted]

Re: How to use interfaces in Go (2012)

#26

Post by ridiculous_fish »

mseepgood wrote: post #18
ridiculous_fish wrote: post #14

When navigating unfamiliar Go codebases, it's hard to know which types fulfill an interface. Say you have a function that takes an Animal; how do you figure out what to call it with? Or to give a concrete example, say you want to do formatted output to stderr. How is one supposed to determine that os.Stderr is something that can be passed to fmt.Fprintf? Is there a better way than manually comparing method signatures…

Use the Go oracle with an "implements" query.

Hey, that's pretty cool. I was able to get it to work, though it is very awkward to use directly (it's designed to be integrated into text editors).

Re: How to use interfaces in Go (2012)

#27

Post by noselasd »

namelezz wrote: post #21
mseepgood wrote: post #18

Earlier quoted context omitted.

Use the Go oracle with an "implements" query.

So beside familiarizing the language syntax, I need to be aware of a set of unofficial tools and plugins, which are likely going to change in the next couple months, to be able to read the code.

"go oracle" is right there with "go build" etc, an official tool that shouldn't change any more than the other tools that's part of the Go distribution.

Re: How to use interfaces in Go (2012)

#28

Post by nothrabannosir »

ridiculous_fish wrote: post #14

When navigating unfamiliar Go codebases, it's hard to know which types fulfill an interface. Say you have a function that takes an Animal; how do you figure out what to call it with? Or to give a concrete example, say you want to do formatted output to stderr. How is one supposed to determine that os.Stderr is something that can be passed to fmt.Fprintf? Is there a better way than manually comparing method signatures…

A pattern that helps with this (tangentially) is to explicitly declare methods to implement an interface at type declaration time:

    type File struct {
        ...
    }
    
    var _ io.Writer = (*File)(nil)
It's not a panacea, but it helps. If you write all your own code this way, at least it will be easy to see which interfaces your own types implement, and (with a grep or GoRef) vice versa.

Plus you get interface implementation checking, so your error messages actually make sense if the interface or type method signatures unexpectedly change.

Again, this is not a real solution to your problem, but it has enough advantages to be worth mentioning.

Re: How to use interfaces in Go (2012)

#29

Post by thwarted »

incepted wrote: post #19
welder wrote: post #2

> func main() { > animals := []Animal{Dog{}, Cat{}, Llama{}, JavaProgrammer{}} > for _, animal := range animals { > fmt.Println(animal.Speak()) > } > } This makes my eyes hurt. In this modern age we still haven't learned to create easy to read languages?

On top of that, the code above ignores errors, something that Go makes all too easy by not supporting exceptions.

This is an extremely contrived critique.

The only place an error could occur in this code is if fmt.Println returns an error. What should happen if you can't display the output? Try to print an error? This is entirely appropriate for demo code and use of stdout like this. No one honors the return value from printf(3) in demo code either. Considering other languages, Python's print functionality doesn't have anything about returning or raising errors, and it wasn't even available as a function until 2.6.

Re: How to use interfaces in Go (2012)

#30

Post by mseepgood »

ridiculous_fish wrote: post #26
mseepgood wrote: post #18

Earlier quoted context omitted.

Use the Go oracle with an "implements" query.

Hey, that's pretty cool. I was able to get it to work, though it is very awkward to use directly (it's designed to be integrated into text editors).

Yes, I use it via vim-go.

You can also use it from a local godoc instance: https://golang.org/lib/godoc/analysis/help.html

And there's Pythia: https://github.com/fzipp/pythia

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