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# gofiber/schema
Package gofiber/schema converts structs to and from form values.
## Example
Here's a quick example: we parse POST form values and then decode them into a struct:
```go
// Set a Decoder instance as a package global, because it caches
// meta-data about structs, and an instance can be shared safely.
var decoder = schema.NewDecoder()
type Person struct {
Name string
Phone string
}
func MyHandler(w http.ResponseWriter, r *http.Request) {
err := r.ParseForm()
if err != nil {
// Handle error
}
var person Person
// r.PostForm is a map of our POST form values
err = decoder.Decode(&person, r.PostForm)
if err != nil {
// Handle error
}
// Do something with person.Name or person.Phone
}
```
Conversely, contents of a struct can be encoded into form values. Here's a variant of the previous example using the Encoder:
```go
var encoder = schema.NewEncoder()
func MyHttpRequest() {
person := Person{"Jane Doe", "555-5555"}
form := url.Values{}
err := encoder.Encode(person, form)
if err != nil {
// Handle error
}
// Use form values, for example, with an http client
client := new(http.Client)
res, err := client.PostForm("http://my-api.test", form)
}
```
To define custom names for fields, use a struct tag "schema". To not populate certain fields, use a dash for the name and it will be ignored:
```go
type Person struct {
Name string `schema:"name,required"` // custom name, must be supplied
Phone string `schema:"phone"` // custom name
Admin bool `schema:"-"` // this field is never set
}
```
The supported field types in the struct are:
* bool
* float variants (float32, float64)
* int variants (int, int8, int16, int32, int64)
* string
* uint variants (uint, uint8, uint16, uint32, uint64)
* struct
* a pointer to one of the above types
* a slice or a pointer to a slice of one of the above types
Unsupported types are simply ignored, however custom types can be registered to be converted.
## Setting Defaults
It is possible to set default values when encoding/decoding by using the `default` tag option. The value of `default` is applied when a field has a zero value, a pointer has a nil value, or a slice is empty.
```go
type Person struct {
Phone string `schema:"phone,default:+123456"` // custom name
Age int `schema:"age,default:21"`
Admin bool `schema:"admin,default:false"`
Balance float64 `schema:"balance,default:10.0"`
Friends []string `schema:friends,default:john|bob`
}
```
The `default` tag option is supported for the following types:
* bool
* float variants (float32, float64)
* int variants (int, int8, int16, int32, int64)
* uint variants (uint, uint8, uint16, uint32, uint64)
* string
* a slice of the above types. As shown in the example above, `|` should be used to separate between slice items.
* a pointer to one of the above types (pointer to slice and slice of pointers are not supported).
> [!NOTE]
> Because primitive types like int, float, bool, unint and their variants have their default (or zero) values set by Golang, it is not possible to distinguish them from a provided value when decoding/encoding form values. In this case, the value provided by the `default` option tag will be always applied. For example, let's assume that the value submitted in the form for `balance` is `0.0` then the default of `10.0` will be applied, even if `0.0` is part of the form data for the `balance` field. In such cases, it is highly recommended to use pointers to allow schema to distinguish between when a form field has no provided value and when a form has a value equal to the corresponding default set by Golang for a particular type. If the type of the `Balance` field above is changed to `*float64`, then the zero value would be `nil`. In this case, if the form data value for `balance` is `0.0`, then the default will not be applied.
## License
BSD licensed. See the LICENSE file for details.
|
