path: root/demos/quickstart/protected/pages/Tutorial/CurrencyConverter.page

<com:TContent ID="body">
	<h1>Building a Simple Currency Converter</h1>
	<p>This tutorial introduces the Prado web application framework and teaches
		you how to build a simple web application in a few simple steps. This
		tutorial assumes that you are familiar with PHP and you have access
		to a web server that is able to serve PHP5 scripts.
	</p> 
	
	<p>In this tutorial you will build a simple web application that converts
		a dollar amount to an other currency, given the rate of that currency 
		relative to the dollar. The completed application is shown bellow.
		<img src=<%~ example2.png %> class="figure" />
		You can try the application <a href="../currency-converter/index.php">locally</a> or at  
		<a href="http://www.pradosoft.com/demos/currency-converter/">Pradosoft.com</a>.
		Notice that the application still functions exactly the same if javascript
		is not available on the user's browser.
	</p>
	
	<h1 id="download">Downloading and Installing Prado</h1>
	<p>To install Prado, simply download the latest version of Prado from
		<a href="http://www.pradosoft.com/">http://www.pradosoft.com</a>
		and unzip the file to a directory <b>not</b> accessible by your web server 
		(you may unzip it to a directory accessible by the web server if you wish
		to see the demos and test). For further detailed installation, see the 
		<a href="?page=GettingStarted.Installation">Quickstart Installation</a> guide.
	</p>
	
	<h1>Creating a new Prado web Application</h1>
	<p>The quickest and simplest way to create a new Prado web application is
		to use the command tool <tt>prado-cli.php</tt> found in the <tt>framework</tt>
		directory of the Prado distribution.  We create a new application by running 
		the  following command in your
		command prompt or console. The command creates a new directory named 
		<tt>currency-converter</tt> in your current working directory.		
		You may need to change to the appropriate directory
		first.
<com:TTextHighlighter Language="text" CssClass="source">
php prado/framework/prado-cli.php -c currency-converter
</com:TTextHighlighter> 
		See the <a href="?page=GettingStarted.CommandLine">Command Line Tool</a> 
		for more details.
	</p>
	
	<p>The above command creates the necessary directory structure and minimal 
		files (including "index.php" and "Home.page") to run a Prado  web application.
		Now you can point your browser's url to the web server to serve up
		the <tt>index.php</tt> script in the <tt>currency-converter</tt> directory.
		You should see the message "Welcome to Prado!" 
	</p>
	
	<h1>Creating the Currency Converter User Interface</h1>
	<p>We start by editing the <tt>Home.page</tt> file found in the 
		<tt>currency-converter/protected/pages/</tt> directory. Files ending
		with ".page" are page templates that contains HTML and Prado controls. 
		We simply add two textboxes, three labels and one button as follows.
<com:TTextHighlighter Language="prado" CssClass="source">
&lt;com:TForm&gt;
    <fieldset>
        <legend>Currency Converter</legend>
        <div class="rate-field">
            &lt;com:TLabel ForControl="currencyRate" Text="Exchange Rate per $1:" /&gt;
            &lt;com:TTextBox ID="currencyRate" /&gt;
        </div>
        <div class="dollar-field">
            &lt;com:TLabel ForControl="dollars" Text="Dollars to Convert:" /&gt;
            &lt;com:TTextBox ID="dollars" /&gt;
        </div>
        <div class="total-field">
            <span class="total-label">Amount in Other Currency:</span>
            &lt;com:TLabel ID="total" CssClass="result" /&gt;
        </div>
        <div class="convert-button">
            &lt;com:TButton Text="Convert" /&gt;
        </div>
    </fieldset>
&lt;/com:TForm&gt;
</com:TTextHighlighter>
	If you refresh the page, you should see something similar to the following figure.
	It may not look very pretty or orderly, but we shall change that later using CSS.
	<img src=<%~ example1.png %> class="figure" />
	</p>
	
	<p>
		The first component we add is a 
		<com:DocLink ClassPath="System.Web.UI.TForm" Text="TForm" />
		that basically corresponds to the HTML <tt>&lt;form&gt;</tt> element.
		In Prado, only <b>one</b> <tt>TForm</tt> element is allowed per page. 
	</p>	
	
	<p>The next two pair of component we add is the 
		<com:DocLink ClassPath="System.Web.UI.WebControls.TLabel" Text="TLabel" />
		and 
		<com:DocLink ClassPath="System.Web.UI.WebControls.TTextBox" Text="TTextBox" />
		that basically defines a label and a textbox for the user of the application
		to enter the currency exchange rate. 
		The <tt>ForControl</tt> property value determines which component
		that the label is for. This allows the user of the application to click
		on the label to focus on the field (a good thing). You could have used
		a plain HTML <tt>&lt;label&gt;</tt> element to do the same thing, but
		you would have to find the correct <tt>ID</tt> of the textbox (or 
		<tt>&lt;input&gt;</tt> in HTML) as Prado components may/will render the 
		<tt>ID</tt> value differently in the HTML output.
	</p>
	
	<p>The next pair of components are similar and defines the textbox
		to hold the dollar value to be converted.
		The <tt>TLabel</tt> with <tt>ID</tt> value "total" defines a simple label.
		Notice that the <tt>ForControl</tt> property is absent. This means that this
		label is simply a simple label which we are going to use to display the
		converted total amount.
	</p>
	
	<p>The final component is a 
		<com:DocLink ClassPath="System.Web.UI.WebControls.TButton" Text="TButton" />
		that the user will click to calculate the results. The <tt>Text</tt>
		property sets the button label.
	</p>
	
	<h1>Implementing Currency Conversion</h1>
	
	<p>If you tried clicking on the "Convert" button then the page will refresh
		and does not do anything else. For the button to do some work, we need
		to add a "Home.php" to where "Home.page" is. The <tt>Home</tt> class
		should extends the
		<com:DocLink ClassPath="System.Web.UI.TPage" Text="TPage" />, the default base
		class for all Prado pages.
<com:TTextHighlighter Language="php" CssClass="source">
&lt;?php
class Home extends TPage
{
	
}
?&gt;
</com:TTextHighlighter>
		Prado uses PHP's <tt>__autoload</tt> method to load classes. The convention
		is to use the class name with ".php" extension as filename. 
	</p>
	
	<p>So far there is nothing interesting about Prado, we just declared some
		"web components" in some template file named Home.page and created
		a "Home.php" file with a <tt>Home</tt> class. The more interesting
		bits are in Prado's event-driven architecture as we shall see next.
	</p>
	
	<p>We want that when the user click on the "Convert" button, we take the
		values in the textbox, do some calculation and present the user with
		the converted total. To handle the user clicking of the "Convert" button
		we simply add an <tt>OnClick</tt> property to the "Convert" button in
	 	the "Home.page" template and add a corresponding event handler method 
		in the "Home.php". 
<com:TTextHighlighter Language="prado" CssClass="source">
&lt;com:TButton Text="Convert" OnClick="convert_clicked" /&gt;
</com:TTextHighlighter>	
		The value of the <tt>OnClick</tt>, "<tt>convert_clicked</tt>", will be the method
		name in the "Home.php" that will called when the user clicks on the 
		"Convert" button.
<com:TTextHighlighter Language="php" CssClass="source">
class Home extends TPage
{
    public function convert_clicked($sender, $param)
    {
        $rate = floatval($this->currencyRate->Text);
        $dollars = floatval($this->dollars->Text);
        $this->total->Text = $rate * $dollars;
    }
}
</com:TTextHighlighter>
		If you run the application in your web browser, enter some values and click
		the "Convert" button then you should see that calculated value displayed next
		to the "Amount in Other Currency" label.
	</p>
	
	<p>In the "<tt>convert_clicked</tt>" method the first parameter, <tt>$sender</tt>,
		corresponds to the object that raised the event, in this case, 
		the "Convert" button. The second parameter, <tt>$param</tt> contains
		any additional data that the <tt>$sender</tt> object may wish to have added.
	</p>
	
	<p>We shall now examine, the three lines that implements the simply currency
		conversion in the "<tt>convert_clicked</tt>" method.
<com:TTextHighlighter Language="php" CssClass="source">
$rate = floatval($this->currencyRate->Text);	
</com:TTextHighlighter>
		The statement <tt>$this->currencyRate</tt> corresponds to the
		<tt>TTextBox</tt> component with <tt>ID</tt> value "currencyRate" in the
		"Home.page" template. The <tt>Text</tt> property of the <tt>TTextBox</tt>
		contains the value that the user entered. So, we obtain this
		value by <tt>$this->currencyRate->Text</tt> which we convert the
		value to a float value.
<com:TTextHighlighter Language="php" CssClass="source">
$dollars = floatval($this->dollars->Text);	
</com:TTextHighlighter>
		The next line does a similar things, it takes the user value from
		the <tt>TTextBox</tt> with <tt>ID</tt> value "dollars and converts it to 
		a float value.
	</p>
	
	<p>The third line calculates the new amount and set this value in the
		<tt>Text</tt> property of the <tt>TLabel</tt> with <tt>ID="total"</tt>.
		Thus, we display the new amount to the user in the label.
<com:TTextHighlighter Language="php" CssClass="source">
$this->total->Text = $rate * $dollars;
</com:TTextHighlighter>	
	</p>
	
	<h1>Adding Validation</h1>
	<p>The way we convert the user entered value to float ensures that the
		total amount is always a number. So the user is free to enter what 
		ever they like, they could even enter letters. The user's experience
		in using the application can be improved by adding validators
		to inform the user of the allowed values in the currency rate and the 
		amount to be calcuated.
	</p>
	
	<p>For the currency rate, we should ensure that
		<ol>
			<li>the user enters a value,</li>
			<li>the currency rate is a valid number,</li> 
			<li>the currency rate is positive.</li>
		</ol>
	 To ensure 1 we add one 
	<com:DocLink ClassPath="System.Web.UI.WebControls.TRequiredFieldValidator" Text="TRequiredFieldValidator" />. To ensure 2 and 3, we add one 
	<com:DocLink ClassPath="System.Web.UI.WebControls.TCompareValidator" Text="TCompareValidator" />. We may add these validators any where within
	the "Home.page" template. Further details regarding these validator and other
	validators can be found in the 
	<a href="?page=Controls.Validation">Validation Controls</a> page.
<com:TTextHighlighter Language="prado" CssClass="source">
&lt;com:TRequiredFieldValidator
	ControlToValidate="currencyRate"
	ErrorMessage="Please enter a currency rate." /&gt;
&lt;com:TCompareValidator
	ControlToValidate="currencyRate"
	DataType="Float"
	ValueToCompare="0"
	Operator="GreaterThan"
	ErrorMessage="Please enter a positive currency rate." /&gt;
</com:TTextHighlighter>
	</p>
		
	<p>For the amount to be calculated, we should ensure that
		<ol>
			<li>the user enters a value,</li>
			<li>the value is a valid number (not including any currency or dollar signs).</li>
		</ol>
	To ensure 1 we just add another <tt>TRequiredFieldValidator</tt>, for 2
	we could use a
	<com:DocLink ClassPath="System.Web.UI.WebControls.TDataTypeValidator" Text="TDataTypeValidator" />. For simplicity we only allow the user to enter
	a number for the amount they wish to convert.
<com:TTextHighlighter Language="prado" CssClass="source">
&lt;com:TRequiredFieldValidator
	ControlToValidate="dollars"
	ErrorMessage="Please enter the amount you wish to calculate." /&gt;
&lt;com:TDataTypeValidator
	ControlToValidate="dollars"
	DataType="Float"
	ErrorMessage="Please enter a number." /&gt;
</com:TTextHighlighter>
	</p>
	
	<p>Now if you try to enter some invalid data in the application or left out
		any of the fields the validators will be activated and present the user
		with error messages. Notice that the error messages are presented
		without reloading the page. Prado's validators by default validates
		using both javascript and server side. The server side validation
		is <b>always performed</b>. For the server side, we
		should skip the calculation if the validators are not satisfied. This can 
		done as follows.
<com:TTextHighlighter Language="php" CssClass="source">
public function convert_clicked($sender, $param)
{
    if($this->Page->IsValid)
    {
        $rate = floatval($this->currencyRate->Text);
        $dollars = floatval($this->dollars->Text);
        $this->total->Text = $rate * $dollars;
    }
}   
</com:TTextHighlighter>     
	</p>
	
	<h1>Improve User Experience With Active Controls</h1>
	<p>In this simple application we may further improve the user experience
		by decreasing the responsiveness of the application. One way to achieve
		a faster response is calculate and present the results without reloading
		the whole page.
	</p>
	
	<p>We can replace the <tt>TButton</tt> with the Active Control counter part,
		<com:DocLink ClassPath="System.Web.UI.ActiveControls.TActiveButton" Text="TActiveButton" />,
		that can trigger a server side click event without reloading the page.
		In addition, we can change the "totals" <tt>TLabel</tt> with the 
		Active Control counter part, 
		<com:DocLink ClassPath="System.Web.UI.ActiveControls.TActiveLabel" Text="TActiveLabel" />, such that the server side can update the browser without
		reloading the page.
<com:TTextHighlighter Language="prado" CssClass="source">
<div class="total-field">
    <span class="total-label">Amount in Other Currency:</span>
         &lt;com:TActiveLabel ID="total" CssClass="result" /&gt;
    </div>
    <div class="convert-button">
        &lt;com:TActiveButton Text="Convert" OnClick="convert_clicked" /&gt;
</div>	
</com:TTextHighlighter>
		The server side logic remains the same, we just need to import the
		Active Controls name space as they are not included by default. We
		add the following line to the begin of "Home.php".
<com:TTextHighlighter Language="php" CssClass="source">
Prado::using('System.Web.UI.ActiveControls.*');	
</com:TTextHighlighter>
	</p>
	
	<p>If you try the application now, you may notice that the page no longer
		needs to reload to calculate and display the converted total amount.
		However, since there is not page reload, there is no indication or not obvious
		that by clicking on the "Convert" button any has happened.
		We can further refine the user experience by change the text of "total" label
		to "calculating..." when the user clicks on the "Convert" button. The text of
		the "total" label will still be updated with the new calculate amount as before.
	</p>
	
	<p>To indicate that the calculation is in progress, we can change the text 
		of the "total" label as follows. We add a <tt>ClientSide.OnLoading</tt> property
		to the "Convert" button (since this button is responsible for requesting
		the calculation).
<com:TTextHighlighter Language="prado" CssClass="source">
&lt;com:TActiveButton Text="Convert" OnClick="convert_clicked" &gt;
    &lt;prop:ClientSide.OnLoading&gt;
        $('&lt;%= $this->total->ClientID %&gt;').innerHTML = "calculating..."
    &lt;/prop:ClientSide.OnLoading&gt;
&lt;/com:TActiveButton&gt;	
</com:TTextHighlighter>
	</p>
	
	<p>The <tt>ClientSide.OnLoading</tt> and various 
	<com:DocLink ClassPath="System.Web.UI.ActiveControls.TCallbackClientSide" Text="other properties" /> accept a javascript block as their content or value. 
	The javascript code <tt>$('...')</tt> is a javascript function that is 
	equivalent to <tt>document.getElementById('...')</tt> that takes a string
	with the ID of an HTML element. Since Prado renders its components's IDs, we need
	to use the rendered ID of the "total" label, that is, <tt>$this->total->ClientID</tt>. We place this bit of code within a <tt>&lt;%= %&gt;</tt> to obtain the rendered HTML ID for the "total" label. The rest of the
	javascript code <tt>innerHTML = "calculating..."</tt> simply changes
	the content of the "total" label.
	</p>
	
	<h1>Adding Final Touches</h1>
	<p>So far we have built a simple currency converter web application with
		little attention of the looks and feel. Now we can add a stylesheet
		to improve the overall appearance of the application. We can simply
		add the stylesheet inline with the template code or we may create
		a "theme".
	</p>
	
	<p>To create and use a theme with Prado applications, we simply create a new
		directory "themes/Basic" in the <tt>currency-converter</tt> directory.
		You may need to create the <tt>themes</tt> directory first. Any
		directory within the <tt>themes</tt> are considered as a theme with the
		name of the theme being the directory name. See the 
		<a href="?page=Advanced.Themes">Themes and Skins</a> for further details.
	</p>
	
	<p>We simply create a CSS file named "common.css" and save it in the
		<tt>themes/Basic</tt> directory. Then we add the following code
		to the beginning of "Home.page" (we add a little more HTML as well).
<com:TTextHighlighter Language="prado" CssClass="source">
&lt;%@ Theme="Basic" %&gt;
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" 	
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" >
&lt;com:THead Title="Currency Converter" /&gt;
<body>	
</com:TTextHighlighter>
		The first line <tt>&lt;%@ Theme="Basic" %&gt;</tt> defines the 
		theme to be used for this page. The 
		<com:DocLink ClassPath="System.Web.UI.WebControls.THead" Text="THead" />
		corresponds to the HTML <tt>&lt;head&gt;</tt> element. In addition
		to display the <tt>Title</tt> property by the <tt>THead</tt>, all CSS
		files in the <tt>themes/Basic</tt> directory are also rendered/linked
		for the current page. Our final currency converter web application
		looks like the following.
		<img src=<%~ example2.png %> class="figure" />
		This completes introduction tutorial to the Prado web application framework.
	</p>
</com:TContent>