Introduction

ccg is a template-based code generation tool for golang.

Install

go get github.com/reusee/ccg/cmd/ccg

Example 0: parameterized types

First define the type

package pair

type T1 interface{}
type T2 interface{}

type Pair struct {
 first  T1
 second T2
}

func New(first T1, second T2) Pair {
 return Pair{first, second}
}

func (p Pair) First() T1 {
 return p.first
}

func (p Pair) Second() T2 {
 return p.second
}

Then put this package to a importable path, assuming $GOPATH/src/pair

Now invoke the ccg command to get type specialized codes

 ccg -f pair -t T1=int,T2=string -r Pair=IntStrPair,New=NewIntStrPair

The above command generates:

type IntStrPair struct {
 first  int
 second string
}

func NewIntStrPair(first int, second string) IntStrPair {
 return IntStrPair{first, second}
}

func (p IntStrPair) First() int {
 return p.first
}

func (p IntStrPair) Second() string {
 return p.second
}

Type T1 and T2 are substituted by int and string. Pair and New are also renamed.

Example 1: output to file / update existing file

Use option -o to write generated codes to a file instead of stdout.

 ccg -f pair -t T1=int,T2=string -r Pair=IntStrPair,New=NewIntStrPair -o foo.go

If the specified file is already exists, ccg will update declarations if they're present in that file, or append to if not. Other non-generated declarations will be preserved.

This means after updating template codes, you can re-invoke the command to update generated codes. So it's friendly to go generate

//go:generate ccg -f pair -t T1=int,T2=string -r Pair=IntStrPair,New=NewIntStrPair -o foo.go

Example 2: partial generation

By default, ccg will generate all declarations from template package (except params). If this is not what you want, you can use -u option to specify what to generate

 ccg -f pair -t T1=int,T2=string -r Pair=IntStrPair,New=NewIntStrPair -u NewIntStrPair,IntStrPair.First

The above command generates:

type IntStrPair struct {
  first  int
  second string
}

func NewIntStrPair(first int, second string) IntStrPair {
  return IntStrPair{first, second}
}

func (p IntStrPair) First() int {
  return p.first
}

Method Second is not generated. And type IntStrPair is automatically generated because it's depended by NewIntStrPair and First method.