Web hosting domain names - CHAPTER 6 DECOUPLED NAVIGATION PATTERN 181 the

CHAPTER 6 DECOUPLED NAVIGATION PATTERN 181 the ConvertToUpperCasefunction is called to convert the case of the text, and the InjectHTML function is called to update the user interface. Looking closer at the OnClickfunction, you can see that the class TextState is instantiated. The purpose of TextState is to define a common state structure for a text buffer and an identifier. The TextStatestructure is passed to and from Action, Data, and Presentation functionalities. The constructor parameters to TextState are the contents of the text box and the destination identifier indicating where the contents are supposed to be injected. The instantiated TextState class is assigned to common.state, which is shared by the still-undefined function InjectHTML. Consider the overall implementation and that the functions OnClick, ConvertToUpperCase, and InjectHTML are independent of each other. The functions share only the common state structure TextState. For example, to implement functionality whereby the contents of the text box are transferred whenever a letter is added to the text box, the OnClick function needs to be replaced. The OnClickfunction could be replaced by capturing the onchange event. The remaining functions would remain identical. Converting the Local Call to a Remote Call The power of decoupling the three functionalities was quickly explained by replacing the OnClick function. What would be more impressive, though, would be to actually go through an example of changing the processing of the data locally to remotely. The remote server call is a service that converts the local text into bold text. Calling the remote server to convert the text is overkill, but the conversion is meant to illustrate the steps of making a remote server call. E B V N URLs Are Componentized Resources Making a remote server call means using XMLHttpRequest, and that requires a URL. When calling a URL, it is important that the URL is well designed. When designing URLs, the objective is to design them as if they were components. Treating URLs as components makes it simpler to modularize the functionality. Some server-side web frameworks for example, ASP.NET and JavaServer Pages (JSP) use the first identifier after the slash to identify an application. For example, the URL /application defines the web application application. The idea that the first identifier specifies an applica tion is not a bad idea, and in fact it is a good idea. For example, imagine implementing both the REST-Based Model View Controller and State Navigation patterns. The two patterns require code that executes in the context of an HTTP server. The two patterns are orthogonal in that they offer different forms of functionality. Because they are orthogonal, there is no real reason why they should share variables, state, or code. The subdivision of applications does not need to stop with applications, but can be extended to components, as illustrated in Figure 6-15. Figure 6-15 shows the root URL /. From the root there are the URLs /search and /state. Each of these URLs represents a resource to a component that implements searching and state navigation functionality. This means that any functionality that starts with /search must relate to search and only search. There cannot be any other type of functionality. Likewise with the URL /state, which means any related URL must relate to implementing state navigation func tionality. If some functionality needs to be implemented that does not relate to the URLs, a new component URL is defined.
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