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2f33fe86f5
* Update dependencies and build to go1.22 * Fix api changes wrt to dependencies * Update golangci config
120 lines
4.5 KiB
Markdown
120 lines
4.5 KiB
Markdown
# gorilla/schema
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[](https://codecov.io/github/gorilla/schema)
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[](https://godoc.org/github.com/gorilla/schema)
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[](https://sourcegraph.com/github.com/gorilla/schema?badge)
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Package gorilla/schema converts structs to and from form values.
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## Example
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Here's a quick example: we parse POST form values and then decode them into a struct:
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```go
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// Set a Decoder instance as a package global, because it caches
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// meta-data about structs, and an instance can be shared safely.
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var decoder = schema.NewDecoder()
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type Person struct {
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Name string
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Phone string
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}
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func MyHandler(w http.ResponseWriter, r *http.Request) {
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err := r.ParseForm()
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if err != nil {
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// Handle error
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}
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var person Person
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// r.PostForm is a map of our POST form values
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err = decoder.Decode(&person, r.PostForm)
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if err != nil {
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// Handle error
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}
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// Do something with person.Name or person.Phone
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}
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```
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Conversely, contents of a struct can be encoded into form values. Here's a variant of the previous example using the Encoder:
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```go
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var encoder = schema.NewEncoder()
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func MyHttpRequest() {
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person := Person{"Jane Doe", "555-5555"}
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form := url.Values{}
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err := encoder.Encode(person, form)
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if err != nil {
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// Handle error
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}
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// Use form values, for example, with an http client
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client := new(http.Client)
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res, err := client.PostForm("http://my-api.test", form)
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}
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```
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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:
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```go
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type Person struct {
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Name string `schema:"name,required"` // custom name, must be supplied
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Phone string `schema:"phone"` // custom name
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Admin bool `schema:"-"` // this field is never set
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}
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```
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The supported field types in the struct are:
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* bool
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* float variants (float32, float64)
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* int variants (int, int8, int16, int32, int64)
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* string
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* uint variants (uint, uint8, uint16, uint32, uint64)
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* struct
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* a pointer to one of the above types
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* a slice or a pointer to a slice of one of the above types
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Unsupported types are simply ignored, however custom types can be registered to be converted.
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## Setting Defaults
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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.
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```go
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type Person struct {
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Phone string `schema:"phone,default:+123456"` // custom name
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Age int `schema:"age,default:21"`
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Admin bool `schema:"admin,default:false"`
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Balance float64 `schema:"balance,default:10.0"`
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Friends []string `schema:friends,default:john|bob`
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}
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```
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The `default` tag option is supported for the following types:
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* bool
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* float variants (float32, float64)
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* int variants (int, int8, int16, int32, int64)
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* uint variants (uint, uint8, uint16, uint32, uint64)
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* string
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* a slice of the above types. As shown in the example above, `|` should be used to separate between slice items.
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* a pointer to one of the above types (pointer to slice and slice of pointers are not supported).
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> [!NOTE]
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> 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.
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## License
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BSD licensed. See the LICENSE file for details.
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