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<com:TContent ID="body"><h1 id="16001">Building a Simple Currency Converter</h1><p id="80053" class="block-content">This tutorial introduces the Prado web application framework and teachesyou how to build a simple web application in a few simple steps. Thistutorial assumes that you are familiar with PHP and you have accessto a web server that is able to serve PHP5 scripts.</p><p id="80054" class="block-content">In this tutorial you will build a simple web application that convertsa dollar amount to an other currency, given the rate of that currencyrelative 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 javascriptis not available on the user's browser.</p><h1 id="download">Downloading and Installing Prado</h1><p id="80055" class="block-content">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 wishto see the demos and test). For further detailed installation, see the<a href="?page=GettingStarted.Installation">Quickstart Installation</a> guide.</p><h1 id="16002">Creating a new Prado web Application</h1><p id="80056" class="block-content">The quickest and simplest way to create a new Prado web application isto 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 runningthe following command in yourcommand 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 directoryfirst.See the <a href="?page=GettingStarted.CommandLine">Command Line Tool</a>for more details.</p><com:TTextHighlighter Language="text" CssClass="source block-content" id="code111">php prado/framework/prado-cli.php -c currency-converter</com:TTextHighlighter><p id="80057" class="block-content">The above command creates the necessary directory structure and minimalfiles (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 upthe <tt>index.php</tt> script in the <tt>currency-converter</tt> directory.You should see the message "Welcome to Prado!"</p><h1 id="16003">Creating the Currency Converter User Interface</h1><p id="80058" class="block-content">We start by editing the <tt>Home.page</tt> file found in the<tt>currency-converter/protected/pages/</tt> directory. Files endingwith ".page" are page templates that contains HTML and Prado controls.We simply add two textboxes, three labels and one button as follows.</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="form1"><com:TForm><fieldset><legend>Currency Converter</legend><div class="rate-field"><com:TLabel ForControl="currencyRate" Text="Exchange Rate per $1:" /><com:TTextBox ID="currencyRate" /></div><div class="dollar-field"><com:TLabel ForControl="dollars" Text="Dollars to Convert:" /><com:TTextBox ID="dollars" /></div><div class="total-field"><span class="total-label">Amount in Other Currency:</span><com:TLabel ID="total" CssClass="result" /></div><div class="convert-button"><com:TButton Text="Convert" /></div></fieldset></com:TForm></com:TTextHighlighter><p id="refresh" class="block-content">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 id="80059" class="block-content">The first component we add is a<com:DocLink ClassPath="System.Web.UI.TForm" Text="TForm" />that basically corresponds to the HTML <tt><form></tt> element.In Prado, only <b>one</b> <tt>TForm</tt> element is allowed per page.</p><p id="80060" class="block-content">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 applicationto enter the currency exchange rate.The <tt>ForControl</tt> property value determines which componentthat the label is for. This allows the user of the application to clickon the label to focus on the field (a good thing). You could have useda plain HTML <tt><label></tt> element to do the same thing, butyou would have to find the correct <tt>ID</tt> of the textbox (or<tt><input></tt> in HTML) as Prado components may/will render the<tt>ID</tt> value differently in the HTML output.</p><p id="80061" class="block-content">The next pair of components are similar and defines the textboxto 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 thislabel is simply a simple label which we are going to use to display theconverted total amount.</p><p id="80062" class="block-content">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 id="16004">Implementing Currency Conversion</h1><p id="80063" class="block-content">If you tried clicking on the "Convert" button then the page will refreshand does not do anything else. For the button to do some work, we needto add a "Home.php" to where "Home.page" is. The <tt>Home</tt> classshould extends the<com:DocLink ClassPath="System.Web.UI.TPage" Text="TPage" />, the default baseclass for all Prado pages.</p><com:TTextHighlighter Language="php" CssClass="source block-content" id="code3"><?phpclass Home extends TPage{}?></com:TTextHighlighter><p id="1111" class="block-content">Prado uses PHP's <tt>__autoload</tt> method to load classes. The conventionis to use the class name with ".php" extension as filename.</p><p id="80064" class="block-content">So far there is nothing interesting about Prado, we just declared some"web components" in some template file named Home.page and createda "Home.php" file with a <tt>Home</tt> class. The more interestingbits are in Prado's event-driven architecture as we shall see next.</p><p id="80065" class="block-content">We want that when the user click on the "Convert" button, we take thevalues in the textbox, do some calculation and present the user withthe converted total. To handle the user clicking of the "Convert" buttonwe simply add an <tt>OnClick</tt> property to the "Convert" button inthe "Home.page" template and add a corresponding event handler methodin the "Home.php".</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="code4"><com:TButton Text="Convert" OnClick="convert_clicked" /></com:TTextHighlighter><p id="222" class="block-content">The value of the <tt>OnClick</tt>, "<tt>convert_clicked</tt>", will be the methodname in the "Home.php" that will called when the user clicks on the"Convert" button.</p><com:TTextHighlighter Language="php" CssClass="source block-content" id="code5">class Home extends TPage{public function convert_clicked($sender, $param){$rate = floatval($this->currencyRate->Text);$dollars = floatval($this->dollars->Text);$this->total->Text = $rate * $dollars;}}</com:TTextHighlighter><div id="3332" class="block-content"><p id="333">If you run the application in your web browser, enter some values and clickthe "Convert" button then you should see that calculated value displayed nextto the "Amount in Other Currency" label.</p><p id="80066">In the "<tt>convert_clicked</tt>" method the first parameter, <tt>$sender</tt>,corresponds to the object that raised the event, in this case,the "Convert" button. The second parameter, <tt>$param</tt> containsany additional data that the <tt>$sender</tt> object may wish to have added.</p><p id="80067">We shall now examine, the three lines that implements the simply currencyconversion in the "<tt>convert_clicked</tt>" method.</p></div><com:TTextHighlighter Language="php" CssClass="source block-content" id="code6" >$rate = floatval($this->currencyRate->Text);</com:TTextHighlighter><p id="444" class="block-content">The statement <tt>$this->currencyRate</tt> corresponds to the<tt>TTextBox</tt> component with <tt>ID</tt> value "currencyRate" in the"Home.page" template. The <tt>Text</tt> property of the <tt>TTextBox</tt>contains the value that the user entered. So, we obtain thisvalue by <tt>$this->currencyRate->Text</tt> which we convert thevalue to a float value.</p><com:TTextHighlighter Language="php" CssClass="source block-content" id="code7">$dollars = floatval($this->dollars->Text);</com:TTextHighlighter><div id="5551" class="block-content"><p id="555">The next line does a similar things, it takes the user value fromthe <tt>TTextBox</tt> with <tt>ID</tt> value "dollars and converts it toa float value.</p><p id="80068">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.</p></div><com:TTextHighlighter Language="php" CssClass="source block-content" id="code8">$this->total->Text = $rate * $dollars;</com:TTextHighlighter><h1 id="16005">Adding Validation</h1><p id="80069" class="block-content">The way we convert the user entered value to float ensures that thetotal amount is always a number. So the user is free to enter whatever they like, they could even enter letters. The user's experiencein using the application can be improved by adding validatorsto inform the user of the allowed values in the currency rate and theamount to be calcuated.</p><p id="80070">For the currency rate, we should ensure that</p><ol id="o111" class="block-content"><li>the user enters a value,</li><li>the currency rate is a valid number,</li><li>the currency rate is positive.</li></ol><p id="666" class="block-content">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 withinthe "Home.page" template. Further details regarding these validator and othervalidators can be found in the<a href="?page=Controls.Validation">Validation Controls</a> page.</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="code9"><com:TRequiredFieldValidatorControlToValidate="currencyRate"ErrorMessage="Please enter a currency rate." /><com:TCompareValidatorControlToValidate="currencyRate"DataType="Float"ValueToCompare="0"Operator="GreaterThan"ErrorMessage="Please enter a positive currency rate." /></com:TTextHighlighter><p id="80071" >For the amount to be calculated, we should ensure that</p><ol id="o222" class="block-content"><li>the user enters a value,</li><li>the value is a valid number (not including any currency or dollar signs).</li></ol><p id="777" class="block-content">To ensure 1 we just add another <tt>TRequiredFieldValidator</tt>, for 2we could use a<com:DocLink ClassPath="System.Web.UI.WebControls.TDataTypeValidator" Text="TDataTypeValidator" />. For simplicity we only allow the user to entera number for the amount they wish to convert.</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="code9a"><com:TRequiredFieldValidatorControlToValidate="dollars"ErrorMessage="Please enter the amount you wish to calculate." /><com:TDataTypeValidatorControlToValidate="dollars"DataType="Float"ErrorMessage="Please enter a number." /></com:TTextHighlighter></p><p id="80072" class="block-content">Now if you try to enter some invalid data in the application or left outany of the fields the validators will be activated and present the userwith error messages. Notice that the error messages are presentedwithout reloading the page. Prado's validators by default validatesusing both javascript and server side. The server side validationis <b>always performed</b>. For the server side, weshould skip the calculation if the validators are not satisfied. This candone as follows.</p><com:TTextHighlighter Language="php" CssClass="source block-content" id="code10" >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><h1 id="16006">Improve User Experience With Active Controls</h1><com:RequiresVersion Version="3.1a" /><p id="80073" class="block-content">In this simple application we may further improve the user experienceby increasing the responsiveness of the application. One way to achievea faster response is calculate and present the results without reloadingthe whole page.</p><p id="80074" class="block-content">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 theActive Control counter part,<com:DocLink ClassPath="System.Web.UI.ActiveControls.TActiveLabel" Text="TActiveLabel" />, such that the server side can update the browser withoutreloading the page.</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="code11"><div class="total-field"><span class="total-label">Amount in Other Currency:</span><com:TActiveLabel ID="total" CssClass="result" /></div><div class="convert-button"><com:TActiveButton Text="Convert" OnClick="convert_clicked" /></div></com:TTextHighlighter><p id="1232" class="block-content">The server side logic remains the same, we just need to import theActive Controls name space as they are not included by default. Weadd the following line to the begin of "Home.php".</p><com:TTextHighlighter Language="php" CssClass="source block-content" id="code12">Prado::using('System.Web.UI.ActiveControls.*');</com:TTextHighlighter><p id="80075" class="block-content">If you try the application now, you may notice that the page no longerneeds to reload to calculate and display the converted total amount.However, since there is not page reload, there is no indication or not obviousthat by clicking on the "Convert" button any has happened.We can further refine the user experience by change the text of "total" labelto "calculating..." when the user clicks on the "Convert" button. The text ofthe "total" label will still be updated with the new calculate amount as before.</p><p id="80076" class="block-content">To indicate that the calculation is in progress, we can change the textof the "total" label as follows. We add a <tt>ClientSide.OnLoading</tt> propertyto the "Convert" button (since this button is responsible for requestingthe calculation).</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="code13"><com:TActiveButton Text="Convert" OnClick="convert_clicked" ><prop:ClientSide.OnLoading>$('<%= $this->total->ClientID %>').innerHTML = "calculating..."</prop:ClientSide.OnLoading></com:TActiveButton></com:TTextHighlighter><p id="80077" class="block-content">The <tt>ClientSide.OnLoading</tt> and various<com:DocLink ClassPath="System.Web.UI.ActiveControls.TCallbackClientSide" Text="other properties" /> accept a javascript block as their content or value.The javascript code <tt>$('...')</tt> is a javascript function that isequivalent to <tt>document.getElementById('...')</tt> that takes a stringwith the ID of an HTML element. Since Prado renders its components's IDs, we needto use the rendered ID of the "total" label, that is, <tt>$this->total->ClientID</tt>. We place this bit of code within a <tt><%= %></tt> to obtain the rendered HTML ID for the "total" label. The rest of thejavascript code <tt>innerHTML = "calculating..."</tt> simply changesthe content of the "total" label.</p><h1 id="16007">Adding Final Touches</h1><p id="80078" class="block-content">So far we have built a simple currency converter web application withlittle attention of the looks and feel. Now we can add a stylesheetto improve the overall appearance of the application. We can simplyadd the stylesheet inline with the template code or we may createa "theme".</p><p id="80079" class="block-content">To create and use a theme with Prado applications, we simply create a newdirectory "themes/Basic" in the <tt>currency-converter</tt> directory.You may need to create the <tt>themes</tt> directory first. Anydirectory within the <tt>themes</tt> are considered as a theme with thename of the theme being the directory name. See the<a href="?page=Advanced.Themes">Themes and Skins</a> for further details.</p><p id="80080" class="block-content">We simply create a CSS file named "common.css" and save it in the<tt>themes/Basic</tt> directory. Then we add the following codeto the beginning of "Home.page" (we add a little more HTML as well).</p><com:TTextHighlighter Language="prado" CssClass="source block-content" id="code14"><%@ Theme="Basic" %><!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" ><com:THead Title="Currency Converter" /><body></com:TTextHighlighter><p id="4334" class="block-content">The first line <tt><%@ Theme="Basic" %></tt> defines thetheme to be used for this page. The<com:DocLink ClassPath="System.Web.UI.WebControls.THead" Text="THead" />corresponds to the HTML <tt><head></tt> element. In additionto display the <tt>Title</tt> property by the <tt>THead</tt>, all CSSfiles in the <tt>themes/Basic</tt> directory are also rendered/linkedfor the current page. Our final currency converter web applicationlooks like the following.<img src=<%~ example2.png %> class="figure" />This completes introduction tutorial to the Prado web application framework.</p><div class="last-modified">$Id: CurrencyConverter.page 1846 2007-04-07 10:35:16Z wei $</div></com:TContent>