Web Development Form Handling and Update Methods Overview

Exploring various form handling and update methods in web development including examples of form structures, Rails form helpers, customization approaches, post-action methods, and security considerations.

• Web development
• Form handling
• Rails
• Update methods
• Security

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Uploaded on Oct 05, 2024 | 0 Views

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1. Simple Form <form action="/product/update" method="post"> Product: <input type="text" name="product"/><br /> Price: <input type="text" name="price" value="49.95"/><br /> <input type="submit" value="Submit"/> </form> CS 142 Lecture Notes: Forms Slide 1

2. Rails Form Helpers Describes type, provides initial values <%= form_for(@student, method: :post, url: {action: :update, id: @student.id}) do |form| %> <%= form.text_field(:name) %> <%= form.text_field(:birth) %> <%= form.submit "Modify Student" %> <% end %> Object representing form <form action="/student/update/4" method="post"> <input id="student_name" name="student[name] size="30" type="text" value="Chen" /> <input id="student_birth" name="student[birth] size="30" type="text" value="1990-02-04" /> <input name="commit" type="submit value="Modify Student" /> </form> Slide 2

3. Customize Format <%= form_for(@student, method: :post, url: {action: :update, id: @student.id}) do |form| %> <table class="form"> <tr> <td><%= form.label(:name, "Name:")%></td> <td><%= form.text_field(:name) %></td> </tr> <tr> <td><%= form.label(:birth, "Date of birth:")%></td> <td><%= form.text_field(:birth) %></td> </tr> ... <table> <%= form.submit "Modify Student" %> <% end %> CS 142 Lecture Notes: Forms Slide 3

4. Post Action Method Hash with all of form data def update @student = Student.find(params[:id]) ]) @student.name = params[:student][:name] @student.birth = params[:student][:birth] @student.gpa = params[:student][:gpa] @student.grad = params[:student][:grad] if @student.save then redirect_to(:action => :show) else render(:action => :edit) end end Redirects on success Redisplay form on error CS 142 Lecture Notes: Forms Slide 4

5. More Compact Approach def update @student = Student.find(params[:id]) if @student.update(params[:student]) then redirect_to(:action => :show) else render(:action => :edit) end end Security checks in Rails 4 cause update to fail CS 142 Lecture Notes: Forms Slide 5

6. Rails 4 Pattern def update @student = Student.find(params[:id]) if @student.update(student_params( params[:student])) then redirect_to(:action => :show) else render(:action => :edit) end end Creates new hash containing only specified elements private def student_params(params) return params.permit(:name, :birth, :gpa, :grad) end CS 142 Lecture Notes: Forms Slide 6

7. Creating New Record def create @student = Student.new(student_params( params[:student]) if @student.save() then redirect_to(:action => :show) else render(:action => :edit) end end CS 142 Lecture Notes: Forms Slide 7

8. Validation (in Model) Built-in validator class Student < ActiveRecord::Base validates_format_of :birth, :with => /\d\d\d\d-\d\d-\d\d/, :message => "must have format YYYY-MM-DD" Custom validation method def validate_gpa if (gpa < 0) || (gpa > 4.0) then errors.add(:gpa, "must be between 0.0 and 4.0") end end Saves error info validate :validate_gpa end CS 142 Lecture Notes: Forms Slide 8

9. Error Messages <% @student.errors.full_messages.each do |msg| %> <p><%= msg %></p> <% end %> <%= form_for(@student, method: :post, url: {action => :update, id: @student.id}) do |form| %> ... <%= form.label(:birth, "Date of birth:")%> <%= form.text_field(:birth) %> ... <% end %> CS 142 Lecture Notes: Forms Slide 9

10. File Uploads with Rails <%= form_for(:student, method: ...) do |form| %> ... <%= form.file_field(:photo) %> ... <% end %> In form post method: params[:student][:photo].read() params[:student][:photo].original_filename CS 142 Lecture Notes: Forms Slide 10

11. CS 142 Lecture Notes: Cookies Slide 11