diff --git a/README.md b/README.md index 821709c..f860ad7 100644 --- a/README.md +++ b/README.md @@ -1,11 +1,18 @@ #Enumer -Enumer generates Go code to get string names from enum values and viceversa. -It is a fork of [Rob Pike’s Stringer tool](https://godoc.org/golang.org/x/tools/cmd/stringer) -but adding a *"string to enum value"* method to the generated code. +Enumer is a tool to generate Go code that adds useful methods Go enums (constants with a specific type) +It started as a fork of [Rob Pike’s Stringer tool](https://godoc.org/golang.org/x/tools/cmd/stringer). -This is useful when you need to read enum values from the command line arguments, from a configuration file, +#Generated functions and methods +When Enumer is applied to a type, it will generate three methods and one function: + +* A method `String()` that returns the string representation of the enum value. This makes the enum conform +the `Stringer` interface, so whenever you print an enum value, you'll get the string name instead of a number. +* A function `String(s string)` to get the enum value from its string representation. This is useful +when you need to read enum values from the command line arguments, from a configuration file, from a REST API request... In short, from those places where using the real enum value (an integer) would -be almost meaningless or hard to trace or use by a human +be almost meaningless or hard to trace or use by a human. +* And two more methods, `MarshalJSON()` and `UnmarshalJSON()`, that makes the enum conform to +the `json.Marshaler` and `json.Unmarshaler` interfaces. Very useful to use it in JSON APIs. For example, if we have an enum type called `Pill`, ```go @@ -19,7 +26,7 @@ const ( Acetaminophen = Paracetamol ) ``` -executing `enumer -type=Pill` will generate a new file with two methods: +executing `enumer -type=Pill` will generate a new file with four methods: ```go func (i Pill) String() string { //... @@ -28,6 +35,14 @@ func (i Pill) String() string { func PillString(s string) (Pill, error) { //... } + +func (i Pill) MarshalJSON() ([]byte, error) { + //... +} + +func (i *Pill) UnmarshalJSON(data []byte) error { + //... +} ``` From now on, we can: ```go @@ -43,11 +58,17 @@ if err != nil { return } // Now pill == Ibuprofen + +// Or marshal/unmarshal to/from json strings + ``` -The generated code is exactly the same as the Stringer tool plus the `String` method, so you can use +The generated code is exactly the same as the Stringer tool plus the mentioned additions, so you can use **Enumer** where you are already using **Stringer** without any code change. ## How to use -The usage of Enumer is the same as Stringer, no changes were introduced. -For more information please refer to the [Stringer docs](https://godoc.org/golang.org/x/tools/cmd/stringer) \ No newline at end of file +The usage of Enumer is the same as Stringer, so you can refer to the [Stringer docs](https://godoc.org/golang.org/x/tools/cmd/stringer) +for more information. +There is only one flag added: `noJSON`. If this flag is set to true (i.e. `enumer -type=Pill -noJSON`), +the JSON related methods won't be generated. +