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Francesc Campoy 2015-02-01 09:37:31 +01:00
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# jsonenums
jsonenums is a tool to automate the creation of methods that satisfy the
`fmt.Stringer`, `json.Marshaler` and `json.Unmarshaler` interfaces.
`json.Marshaler` and `json.Unmarshaler` interfaces.
Given the name of a (signed or unsigned) integer type T that has constants
defined, stringer will create a new self-contained Go source file implementing
defined, jsonenums will create a new self-contained Go source file implementing
```
func (t T) String() string
func (t T) MarshalJSON() ([]byte, error)
func (t *T) UnmarshalJSON([]byte) error
```
@ -43,19 +42,23 @@ in the same directory will create the file `pill_jsonenums.go`, in package
`painkiller`, containing a definition of
```
func (r Pill) String() string
func (r Pill) MarshalJSON() ([]byte, error)
func (r *Pill) UnmarshalJSON([]byte) error
```
That method will translate the value of a Pill constant to the string
`MarshalJSON` will translate the value of a `Pill` constant to the `[]byte`
representation of the respective constant name, so that the call
`fmt.Print(painkiller.Aspirin) will print the string "Aspirin".
`json.Marshal(painkiller.Aspirin) will return the bytes `[]byte("\"Aspirin\"")`.
`UnmarshalJSON` performs the opposite operation; given the `[]byte`
representation of a `Pill` constant it will change the receiver to equal the
corresponding constant. So given `[]byte("\"Aspirin\"")` the receiver will
change to `Aspirin` and the returned error will be `nil`.
Typically this process would be run using go generate, like this:
```
//go:generate stringer -type=Pill
//go:generate jsonenums -type=Pill
```
If multiple constants have the same value, the lexically first matching name
@ -66,6 +69,6 @@ the arguments must name a single directory holding a Go package or a set of Go
source files that represent a single Go package.
The `-type` flag accepts a comma-separated list of types so a single run can
generate methods for multiple types. The default output file is t_string.go,
generate methods for multiple types. The default output file is t_jsonenums.go,
where t is the lower-cased name of the first type listed. THe suffix can be
overridden with the `-suffix` flag.