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Difference "Tutorial: Start with forms" ver. 2 versus ver. 3

Content:

Now we learn how to use forms.

## Create form

First we create our simple form, edit `data.h` file and add header:

#include <cppcms/form.h>

Then create a form class derived from `cppcms::form`:

struct info_form : public cppcms::form {

Then we add widgets to this form:

widgets::text name;

widgets::radio sex;

widgets::select martial;

widgets::number<double> age;

widgets::submit submit;

Where, `text` is text input field, `radio` is multiple choice field, `select` is drop down list of choices, `number<>` is number of specific type and `submit` is submit button.

Now we create a constructor for our class:

info_form() :

name("name","Your Name"),

sex("sex","Sex"),

martial("mat","martial State"),

age("age","Your Age"),

submit("submit","Send")

{

First we call constructors of all our widgets. First parameter is usually `name` HTML field and the second is Description, or value in case of `submit`.

Then we must register all our widgets to this form

*this & name & sex & martial & age & submit;

This allows centralized rendering, loading and validation

of the form. Then we add different conditions and configurations to our widgets:

sex.add("Male");

sex.add("Female");

martial.add("Single");

martial.add("Married");

martial.add("Divorced");

Adding different options of selection fields.

name.set_nonempty();

age.set_range(0,120);

Define limits: name should not be empty and age should be in range of 0--120.

And now we can add it to our content class (with some other fields for future use).

struct message : public base_content {

string name,state,sex;

double age;

info_form info;

};

## Form in templates

First we create our output

<% if not empty name %>

<h1>Hello <% name %></h1>

<p>You are <% sex %>, <% state %></p>

<p>Your age is <% age %></p>

<% else %>

<h1>Input your details</h1>

<% end %>

Then we put our form using tag `<% form as_p info %>`:

<form method="post" action="" >

<% form as_p info %>

</form>

The flag `as_p` tells to render form `info` using paragraphs.

## Working with form in code:

First we create our content that contains required

form.

data::message c;

Then we test, if something was send:

if(env->getRequestMethod()=="POST") {

If so we load our form and validate it:

c.info.load(*cgi);

if(c.info.validate()) {

if the form is valid, we can do anything

we want. For example setup our content

fields with appropriate values from the form.

c.name=c.info.name.get();

c.sex=c.info.sex.get();

c.state=c.info.martial.get();

c.age=c.info.age.get();

We clear it at the end, because we want user to

put new values

c.info.clear();

Now we can render our template as usual:

} // if valid

} // if post

render("message",c);

## Additional Validation

Let's assume that standard widgets checks are not good enough. We can extend our validation manually.

For example, I want to make sure that person can't be married if his age under 18. We override `validate()` virtual function that does the job:

virtual bool validate()

{

if(!form::validate()) return false;

if(martial.get()!="Single" && age.get()<18) {

martial.not_valid();

return false;

}

return true;

}

First we validate form as usual with `form::validate()`

and then we do our tests, if something is incorrect,

we mark the filed `martial` as not valid, and this would

be visible in rendered HTML form.

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