Server Side form validation 3

internal/forms/forms.go

@@ -1,8 +1,10 @@
 package forms
 
 import (
+	"fmt"
 	"net/http"
 	"net/url"
+	"strings"
 )
 
 // Form creates a custom form struct, embeds a url.Values object
@@ -19,17 +21,33 @@ func New(data url.Values) *Form {
 	}
 }
 
+// Required checks required fields
+func (f *Form) Required(fields ...string) {
+    for _, field := range fields {
+        value := f.Get(field)
+        if strings.TrimSpace(value) == "" {
+            f.Errors.Add(field, "This field cannot be blank")
+        }
+    }
+}
+
 // Has checks if form field is in post and not emtpy
 func (f *Form) Has(field string, r *http.Request) bool {
 	x := r.Form.Get(field)
-	if x == "" {
+    return x != ""
-		f.Errors.Add(field, "This field cannot be blank")
-		return false
-	}
-	return true
 }
 
 // Valid returns true if there are no errors, otherwise false
 func (f *Form) Valid() bool {
 	return len(f.Errors) == 0
 }
+
+// MinLength checks for string minimum length
+func (f *Form) MinLength(field string, length int, r *http.Request) bool {
+    value := r.Form.Get(field)
+    if len(value) < length {
+        f.Errors.Add(field, fmt.Sprintf("This field must have at least %d letters", length))
+        return false
+    }
+    return true
+}

internal/handlers/handlers.go

@@ -69,8 +69,16 @@ func (m *Repository) Majors(w http.ResponseWriter, r *http.Request) {
 
 // MakeReservation is the make reservation page handler
 func (m *Repository) MakeReservation(w http.ResponseWriter, r *http.Request) {
+    // For the first time render emptyReservation so that this object is
+    // filled with the info when sent back.
+    var emptyReservation models.Reservation
+    data := make(map[string]interface{})
+
+    data["reservation"] = emptyReservation
+
 	render.RenderTemplate(w, r, "make-reservation.page.tmpl", &models.TemplateData{
 		Form: forms.New(nil),
+        Data: data,
 	})
 }
 
@@ -91,7 +99,8 @@ func (m *Repository) PostMakeReservation(w http.ResponseWriter, r *http.Request)
 
 	form := forms.New(r.PostForm)
 
-	form.Has("first_name", r)
+	form.Required("first_name", "last_name", "email")
+    form.MinLength("first_name", 2, r)
 
 	if !form.Valid() {
 		data := make(map[string]interface{})

templates/make-reservation.page.tmpl

@@ -5,6 +5,7 @@
         <div class="col">
             <h1 class="text-center mt-3">Make reservation</h1>
 
+            {{$res := index .Data "reservation"}}
             <!-- <form method="post" action="" class="needs-validation" novalidate> -->
             <form method="post" action="" class="" novalidate>
                 <input type="hidden" name="csrf_token" value="{{.CSRFToken}}">
@@ -15,19 +16,27 @@
                     <label class="text-danger">{{.}}</label>
                     {{end}}
                     <input type="text" name="first_name" id="first_name" class="form-control {{with .Form.Errors.Get "first_name"}} is-invalid {{end}}"
-                        required autocomplete="off">
+                        value="{{$res.FirstName}}" required autocomplete="off">
                 </div>
                 <div class="form-group mt-5">
                     <label for="last_name">Last name:</label>
-                    <input type="text" name="last_name" id="last_name" class="form-control" required autocomplete="off">
+                    {{with .Form.Errors.Get "last_name"}}
+                    <label class="text-danger">{{.}}</label>
+                    {{end}}
+                    <input type="text" name="last_name" id="last_name" class="form-control {{with .Form.Errors.Get "last_name"}} is-invalid {{end}}"
+                        value="{{$res.LastName}}" required autocomplete="off">
                 </div>
                 <div class="form-group mt-5">
                     <label for="email">Email:</label>
-                    <input type="email" name="email" id="email" class="form-control" required autocomplete="off">
+                    {{with .Form.Errors.Get "email"}}
+                    <label class="text-danger">{{.}}</label>
+                    {{end}}
+                    <input type="email" name="email" id="email" class="form-control {{with .Form.Errors.Get "email"}} is-invalid {{end}}"
+                        value="{{$res.Email}}" required autocomplete="off">
                 </div>
                 <div class="form-group mt-5">
                     <label for="phone">Phone number:</label>
-                    <input type="text" name="phone" id="phone" class="form-control" required autocomplete="off">
+                    <input type="text" name="phone" id="phone" class="form-control" value="{{$res.Phone}}" autocomplete="off">
                 </div>
 
                 <hr>