test: add package example

examples/json.go

@@ -0,0 +1,49 @@
+package examples
+
+import (
+	"encoding/json"
+	"fmt"
+
+	"github.com/LukaGiorgadze/gonull"
+)
+
+type MyCustomInt int
+type MyCustomFloat32 float32
+
+type Person struct {
+	Name    string                           `json:"name"`
+	Age     gonull.Nullable[MyCustomInt]     `json:"age"`
+	Address gonull.Nullable[string]          `json:"address"`
+	Height  gonull.Nullable[MyCustomFloat32] `json:"height"`
+}
+
+func Example() {
+	jsonData := []byte(`{"name":"Alice","age":15,"address":null,"height":null}`)
+
+	var person Person
+	if err := json.Unmarshal(jsonData, &person); err != nil {
+		panic(err)
+	}
+
+	// Age is present and valid.
+	fmt.Printf("Person.Age is valid: %t, present: %t\n", person.Age.Valid, person.Age.Present)
+
+	// Address is present but invalid (explicit null).
+	fmt.Printf("Person.Address is valid: %t, present: %t\n", person.Address.Valid, person.Address.Present)
+
+	// Same for the height.
+	fmt.Printf("Person.Height is valid: %t, present: %t\n", person.Height.Valid, person.Height.Present)
+
+	marshalledData, err := json.Marshal(person)
+	if err != nil {
+		panic(err)
+	}
+	// Null values will be kept when marshalling to JSON.
+	fmt.Println(string(marshalledData))
+
+	// Output:
+	// Person.Age is valid: true, present: true
+	// Person.Address is valid: false, present: true
+	// Person.Height is valid: false, present: true
+	// {"name":"Alice","age":15,"address":null,"height":null}
+}