c# print barcode zebra printer xiii in Objective-C

Integrating barcode data matrix in Objective-C xiii

In Java, all collection classes are mutable. It s possible to create an immutable collection using a special method like java.util.Collections.unmodifiableCollection(Collection), but that s rare. For the most part, you design your code with the assumption that all collections are mutable, paying special attention to when collections are passed by reference to other methods. Most Objective-C collection classes adhere to an immutable base class, mutable subclass design pattern. The base classes of the traditional collection classes (NSArray, NSDictionary, NSSet, and NSIndexSet) are truly immutable. They lack any methods that can modify the collection. When a method accepts or returns one of these classes, it is implicitly immutable removing most pass-byreference concerns that Java programmers contend with. You might be wondering just how useful an immutable collection class is, but they re quite handy. They use many of the same programming patterns as java.lang.String objects. To interactively construct or manipulate a collection, you must create one of the mutable subclasses: NSMutableArray, NSMutableDictionary, NSMutableSet, or NSMutableIndexSet. These subclasses define all of the methods used to alter the contents of the collection. Being subclasses, you can pass any mutable collection object as an immutable type. However, you should take some care when doing this. In Objective-C, the receiver of an immutable collection will likely assume it to be immutable, whereas in Java it would rightly assume it to be mutable. If the receiver keeps a reference to the original object, it may behave erratically if its immutable collection is arbitrarily altered. You can safely pass mutable collections as immutable collections as long as nothing else modifies the collection, or the receiver understands that it might actually be a mutable collection. Otherwise, convert the collection into an immutable collection using one of the lightweight collection copy constructors. To make immutable classes useful and easy to work with, Objective-C provides an extensive set of constructors and methods that create and return an immutable collection. These convenience constructors make it easy to create immutable copies of other collections or make a single change to an immutable collection by creating a new collection. The immutable collection constructors are listed in Table 16-2. Table 16-2. Immutable Collection Constructors

This will dump out all of the static members on the .NET System.String class. If you want to call one of these methods, you need to use the :: operator. Let s use the join method to join an array of string. First create the array: BASIC TYPES AND LITERALS 77

Listing 1.7 Hello LINQ in VB.NET (HelloLinq.vbproj)

Assignment in C# Table A.5 presents the C# assignment operators. Like C/C++, C# provides compound assignment operators of the form a op= b. In general, a op= b, where op is an arithmetic operator, is just a convenient shorthand for a = a op b.

To understand how you can use the NHibernate ISession, let s consider its relationship with transactions. Previously, we ve discussed two related concepts:

Aside from providing references to the appropriate namespaces and providing a place to put resources (the Application.Resources tag), the important item here is the StartupUri attribute. It tells WPF what window to start up. You can also provide other attributes here like the following:

<Rectangle Stroke="Black" Width="104" Height="64" Canvas.Left="8" Canvas.Top="8" RadiusX="15" RadiusY="50"/>

The stored procedure uses the XMLHTTP component included with the Microsoft XML Parser (MSXML) to invoke the Campaigner Web service. (If you need more background information about this technology, see the Resources section at the end of this book.) WEB SERVICE ACCESS (SOAP) IN ACTION 381

return;

Figure 11.6 The Copy Files tab lets you specify the log backup copy location, frequency, and retention period.

Summary