java code 39 barcode JAVASCRIPT RECIPES in Font

Creator USS Code 39 in Font JAVASCRIPT RECIPES

CHAPTER 2 JAVASCRIPT RECIPES
Printing ANSI/AIM Code 39 In None
Using Barcode printer for Font Control to generate, create Code 3 of 9 image in Font applications.
www.OnBarcode.com
Make Barcode In None
Using Barcode generation for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
This source code is an example of how not to write a Proxy pattern implementation. The problem of the implementation is shown in the bold code. At the beginning of the bold code are two eval statements, which are generating the values of the generatedOrigFunc and generatedProxyFunc variables. In the embedded function instance[funcIdentifier], the variables are referenced, and due to closure, the origFunc and proxyFunc variables will reference the correct variables. The concept of the Proxy pattern is that when a method is called, it first calls the function referenced by proxyFunc, which then calls the function referenced by origFunc. Because proxyFunc is called first, it has the ability to preprocess or postprocess the data. The code as written will work with a single application of the Proxy pattern, but it will fail if the proxy pattern is applied multiple times. For example, imagine the generated code embedding of the Proxy pattern on an already applied Proxy pattern. Figure 2-3 shows two instances of the proxy code, and in one instance the generatedOrigFunc variable is referencing the other proxy code instance. This code is an example of a gotcha piece of code in JavaScript. Look closely at the declarations of the generatedOrigFunc and generatedProxyFunc variables what are they referencing
Making UPC Symbol In None
Using Barcode generation for Font Control to generate, create UPCA image in Font applications.
www.OnBarcode.com
Encoding Code 39 In None
Using Barcode drawer for Font Control to generate, create Code 39 image in Font applications.
www.OnBarcode.com
Figure 2-3. Multiple embedding of the proxy pattern
GS1 128 Creator In None
Using Barcode maker for Font Control to generate, create EAN 128 image in Font applications.
www.OnBarcode.com
Create Barcode In None
Using Barcode drawer for Font Control to generate, create Barcode image in Font applications.
www.OnBarcode.com
CHAPTER 2 JAVASCRIPT RECIPES
Make PDF-417 2d Barcode In None
Using Barcode printer for Font Control to generate, create PDF-417 2d barcode image in Font applications.
www.OnBarcode.com
Intelligent Mail Encoder In None
Using Barcode creation for Font Control to generate, create 4-State Customer Barcode image in Font applications.
www.OnBarcode.com
To understand the error, think of the proxy code on the left as proxy implementation 1 (PI1) and the code on the right as proxy implementation 2 (PI2). If a generic caller were to call PI1, the following sequence of events would take place: 1. PI1 is called. 2. PI1 s proxyFunc is called. 3. PI1 s origFunc is called, which is PI2. 4. PI2 s proxyFunc is called, which is PI1 s proxyFunc. 5. PI1 s proxyFunc is called, calling PI1 s origFunc. Following these steps, you will notice that a recursion is taking place. The recursion is because of the way the generatedOrigFunc and generatedProxyFunc variables are declared. These variables are declared without any scope and because the proxy scope function is a mix of using references with eval code. This is a bad practice, because some variables will be serialized and others will not. We want a solution like the C preprocessor, where generics represent the physical replacing of an identifier with a desired type. We don t want a templating system. A templating system would be described as follows: <%for( var count = 0; count < 10; count ++) {%> series[<%=count%>] = GenSeries( <%=count%>) <%}%> This isn t what we want because the code readability decreases dramatically, and in general it is not necessary. JavaScript is a dynamic code language, and many of the templating constructs can be implemented in code. It s more difficult to implement the changing of a variable from using references to using values.
ANSI/AIM Code 39 Generation In Java
Using Barcode drawer for Android Control to generate, create Code 39 Full ASCII image in Android applications.
www.OnBarcode.com
Decode USS Code 39 In C#.NET
Using Barcode recognizer for VS .NET Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Solution
EAN / UCC - 13 Printer In Java
Using Barcode printer for BIRT reports Control to generate, create European Article Number 13 image in Eclipse BIRT applications.
www.OnBarcode.com
Generating Universal Product Code Version A In None
Using Barcode creator for Online Control to generate, create UPC Symbol image in Online applications.
www.OnBarcode.com
For illustration purposes, let s simplify the Proxy pattern to a single method with a single method call, as follows. Source: /website/ROOT/ajaxrecipes/javascript/generics.html function EmbeddedReplace() { var func = __toCall; info( "Replace", "hello"); func(); } The EmbeddedReplace function has declared a local variable, func. The func local variable references the __toCall variable. After the declaration of func is a call to the info function. The last function call is to func, which is a function call to __toCall. From looking solely at the usage of __toCall, you don t know much about the declaration other than it s a global variable. For the scope of this recipe, __toCall is an identifier that will be replaced. A JavaScript expansion call would be as follows (I ll discuss the details shortly):
PDF-417 2d Barcode Drawer In Java
Using Barcode encoder for Java Control to generate, create PDF-417 2d barcode image in Java applications.
www.OnBarcode.com
Creating QR Code ISO/IEC18004 In Objective-C
Using Barcode generator for iPhone Control to generate, create Quick Response Code image in iPhone applications.
www.OnBarcode.com
CHAPTER 2 JAVASCRIPT RECIPES
Encode Code 39 Full ASCII In VS .NET
Using Barcode generator for ASP.NET Control to generate, create USS Code 39 image in ASP.NET applications.
www.OnBarcode.com
Creating Matrix In C#
Using Barcode generation for .NET Control to generate, create 2D Barcode image in VS .NET applications.
www.OnBarcode.com
EmbeddedReplace = Generics.expand( EmbeddedReplace, { __toCall: function() { info( "replaced in Replace", "hello");}}); EmbeddedReplace(); The Generics.expand method has two parameters. The first parameter is the EmbeddedReplace function, which will have its implementation modified. The second parameter is the object structure that represents what identifiers will be replaced. The object structure is defined such that the property identifier defines the identifier to be replaced, and the value associated with the property is the replaced value.
PDF 417 Decoder In Java
Using Barcode decoder for Java Control to read, scan read, scan image in Java applications.
www.OnBarcode.com
Draw EAN13 In .NET Framework
Using Barcode encoder for Visual Studio .NET Control to generate, create EAN 13 image in VS .NET applications.
www.OnBarcode.com
Note All of the code presented here uses standard JavaScript programmatic techniques. You don t need
Code-39 Creator In Java
Using Barcode generation for Android Control to generate, create USS Code 39 image in Android applications.
www.OnBarcode.com
ANSI/AIM Code 128 Encoder In Visual Studio .NET
Using Barcode maker for .NET Control to generate, create Code 128 Code Set A image in Visual Studio .NET applications.
www.OnBarcode.com
to use special buffers or tags that confuse editors and make it more complicated to build reliable, maintainable code.
When the Generics.expand method has finished executing, the following function declaration is generated: function GeneratedEmbeddedReplace() { var func = (function () { info("replaced in Replace", "hello"); }); info("Replace", "hello"); func(); } The generated buffer is what we expect, and the behavior is what we expect. When GeneratedEmbeddedReplace is called, the embedded function is called. For comparison s sake, let s look at how this could have worked without expanding an embedded function: function __toCall() { info("replaced in Replace", "hello"); }; function EmbeddedReplace() { var func = __toCall; info( "Replace", "hello"); func(); } Calling GeneratedEmbeddedReplace will call the __toCall function and behave, look, and feel like the expanded example. But why should you do this The reference-based expansion is not an expansion at all. You have simply created a global variable (__toCall) that can be assigned at runtime. With a value-type expansion, you can have multiple functions with different functionalities that do not conflict with one another. Because behavior is determined by assignment, you can run into the situation outlined in Recipe 2-14, where functions are shared. If functions are shared, then a conflict can arise if the functionality of the function is altered. Or you can have a situation where a function does one
Copyright © OnBarcode.com . All rights reserved.