Documentation On “All Known Implementation” of Interfaces

Question

Few months into learning Go, I just discover that os.File implements the io.Reader interface by implementing the Read(b []byte) (n int, err error) function. This allows me to us

Answer 1

https://github.com/dominikh/implements can do this:

implements is a command line tool that will tell you which types implement which interfaces, or which interfaces are implemented by which types.

e.g.

~ implements -types=crypto/cipher
crypto/cipher.StreamReader implements...
        io.Reader
*crypto/cipher.StreamReader implements...
        io.Reader
crypto/cipher.StreamWriter implements...
        io.Closer
        io.WriteCloser
        io.Writer
*crypto/cipher.StreamWriter implements...
        io.Closer
        io.WriteCloser
        io.Writer

Answer 2

For all you vim junkies out there, vim-go supports advance code analysis using the :GoImplements, :GoCallees, :GoChannelPeers, :GoReferrers etc. oracle commands.

For example, if I have a Calculator interface and implementation that looks like:

type Arithmetic interface{
  add(float64, float64) float64 
}

type Calculator struct{}

func (c *calculator) add(o1, o2 float64) float64 {
  // ... stuff
}

Then running :GoImplements in vim with my cursor on the type Arithmetic interface will yield something like:

calculator.go|8 col 6| interface type Arithmetic
calculator.go|3 col 6| is implemented by pointer type *calculator

Now if I moved my cursor to the type Calculator struct{} line and run :GoImplements, I will get something like:

calculator.go|3 col 6| pointer type *calculator
calculator.go|8 col 6| implements Arithmetic

Note: If you got an "unknown command" error, try execute :GoInstallBinaries first before re-trying.

Answer 3

You can find the info you want and more using the godoc command's static analysis tools. Run the following at the command line: godoc -http=":8080" -analysis="type". Using the documentation you can find out what types implement an interface and the method set for a type.

There is also a pointer analysis that allows you to find callers and callees of various types. The channel send<--->receive analysis is pretty neat.

You can also read more about the static analysis done by the godoc tool at http://golang.org/lib/godoc/analysis/help.html