native barcode generator for crystal reports SPECIAL MEMBER FUNCTIONS AND RESOURCE MANAGEMENT in Visual C#.NET

Generator ECC200 in Visual C#.NET SPECIAL MEMBER FUNCTIONS AND RESOURCE MANAGEMENT

CHAPTER 6 SPECIAL MEMBER FUNCTIONS AND RESOURCE MANAGEMENT
Data Matrix Creation In C#
Using Barcode drawer for .NET framework Control to generate, create Data Matrix image in .NET framework applications.
www.OnBarcode.com
Reading Data Matrix ECC200 In C#.NET
Using Barcode decoder for .NET framework Control to read, scan read, scan image in .NET framework applications.
www.OnBarcode.com
Copy constructors are often called implicitly to pass method arguments. As an example, assume the following method: void f(auto_handle<T> t); The following code can be used to call f: auto_handle<T> t = gcnew T(); f(t); Before f is called, the parameter t is copied on the stack via the copy constructor. Since auto_handle s copy constructor is implemented so that only one auto_handle refers to an object, an auto_handle variable will wrap a nullptr handle after it is passed into a function call to f. You should define functions with auto_handle parameters only if you intend to pass the responsibility for cleaning up the wrapped object from the calling method to the called method. It is also possible to define methods that return an auto_handle type. To understand the use case for auto_handle return types, it makes sense to review the GetFile function in the sample code shown previously. FileStream^ GetFile() { return gcnew FileStream("sample.txt", FileMode::Open); } GetFile expects the caller to dispose the returned FileStream object. However, there is nothing in the signature of this function that can be seen as a hint to this fact. In order to find this out, you have to look into the documentation or, in the worst case, you have to reverseengineer the GetFile function with ILDASM or another tool. If you don t make sure you know about the semantics of the functions you call, you will likely end up disposing expensive objects either twice or not at all. Neither situation is desired. The following code shows how the GetFile method can be modified so that its signature clearly states that the caller is supposed to do the cleanup: auto_handle<FileStream> GetFile() { FileStream^ fs = gcnew FileStream("sample.txt", FileMode::Open); return auto_handle<FileStream>(fs); } In this version of GetFile, the return type is an auto_handle. If you see such a function, it is unambiguous that the caller of GetFile is responsible for disposing the wrapped object. The constructor of the auto_handle is called to build the auto_handle object that is returned. For methods that are used only inside your assembly (methods of private classes or methods of public classes with private, internal, or private protected visibility), it is recommended to use the auto_handle as a return type if the caller is supposed to dispose the returned object. However, it must also be mentioned that you cannot use this pattern across assembly boundaries. You can use auto_handle in method signatures only if the calling function and the called function are in the same assembly. For methods that can be called outside the assembly, you must use a tracking handle type instead of an auto_handle, even though this is less expressive.
Print ECC200 In C#
Using Barcode encoder for .NET framework Control to generate, create Data Matrix image in VS .NET applications.
www.OnBarcode.com
2D Barcode Creator In Visual C#
Using Barcode generator for .NET framework Control to generate, create Matrix image in VS .NET applications.
www.OnBarcode.com
CHAPTER 6 SPECIAL MEMBER FUNCTIONS AND RESOURCE MANAGEMENT
Generate UPC-A In Visual C#
Using Barcode maker for .NET Control to generate, create UCC - 12 image in Visual Studio .NET applications.
www.OnBarcode.com
Generating Linear 1D Barcode In C#
Using Barcode drawer for Visual Studio .NET Control to generate, create Linear Barcode image in .NET applications.
www.OnBarcode.com
Copy Constructors and Assignment Operators
Generate PDF 417 In Visual C#.NET
Using Barcode drawer for .NET Control to generate, create PDF 417 image in Visual Studio .NET applications.
www.OnBarcode.com
ANSI/AIM Codabar Drawer In C#
Using Barcode generator for VS .NET Control to generate, create ABC Codabar image in Visual Studio .NET applications.
www.OnBarcode.com
The CLR implicitly provides a bitwise initialization and assignment behavior for managed values. When a tracking handle is initialized from another tracking handle, the source handle s binary data (the pointer referring into the object s header) is just copied to the target. This is shown in the following code: FileStream^ fs = GetFile(); // no copy constructor called - handle itself is just copied FileStream^ fs2 = fs; FileStream^ fs3; // no assignment operator called handle itself is just copied fs3 = fs2; If you just stick with tracking handles and managed values for value type instances, you will never have to use a copy constructor or an assignment operator. Copy constructors and assignment operators of managed types are used only in the context of the implicitly dereferenced syntax. The copy constructor of a ref class R is only called when an implicitly dereferenced variable of type R is initialized with an expression of the same type or of type R%. The following code shows the first case: // construct a new auto handle from a tracking handle auto_handle<FileStream> fs = GetFile(); // copy constructor called auto_handle<FileStream> fs2 = fs; This sample uses the implicitly dereferenced syntax to define the two variables fs and fs2 of the ref class auto_handle<FileStream>. To initialize fs2 with the implicitly dereferenced variable fs, the copy constructor of auto_handle<FileStream> is called. Since the implicitly dereferenced syntax is a special feature of C++/CLI, copy constructors and assignment operators are not language interoperable. However, they are necessary to implement helper classes like auto_handle. To explain these special member functions in a concrete context, I will discuss how they are implemented in the auto_handle template. A copy constructor of a native type N must have exactly one argument of either N& or const N&. Likewise, a copy constructor of a ref class R must have an argument of type R% or const R%. auto_ptr s copy constructor is implemented as follows: auto_handle(auto_handle<_element_type> % _right ) : m_handle( _right.release() ) { } _element_type ^ release() { _element_type ^_tmp_ptr = m_handle; m_handle = nullptr; return _tmp_ptr; }
Recognize Data Matrix ECC200 In Visual C#
Using Barcode decoder for VS .NET Control to read, scan read, scan image in .NET applications.
www.OnBarcode.com
DataMatrix Encoder In Java
Using Barcode generation for BIRT reports Control to generate, create Data Matrix image in BIRT reports applications.
www.OnBarcode.com
QR Code Encoder In .NET
Using Barcode drawer for Reporting Service Control to generate, create QR Code image in Reporting Service applications.
www.OnBarcode.com
Encoding Barcode In Java
Using Barcode printer for BIRT reports Control to generate, create Barcode image in Eclipse BIRT applications.
www.OnBarcode.com
PDF417 Generation In VS .NET
Using Barcode encoder for Visual Studio .NET Control to generate, create PDF 417 image in .NET framework applications.
www.OnBarcode.com
Painting QR Code JIS X 0510 In None
Using Barcode creation for Microsoft Word Control to generate, create QR Code image in Office Word applications.
www.OnBarcode.com
UPC-A Supplement 2 Creator In Java
Using Barcode drawer for Java Control to generate, create GTIN - 12 image in Java applications.
www.OnBarcode.com
Encoding Code 128 Code Set C In None
Using Barcode drawer for Software Control to generate, create Code 128 Code Set A image in Software applications.
www.OnBarcode.com
Printing QR Code In Java
Using Barcode drawer for Java Control to generate, create QR Code ISO/IEC18004 image in Java applications.
www.OnBarcode.com
Print Barcode In VS .NET
Using Barcode printer for ASP.NET Control to generate, create Barcode image in ASP.NET applications.
www.OnBarcode.com
Barcode Drawer In None
Using Barcode generator for Software Control to generate, create Barcode image in Software applications.
www.OnBarcode.com
ECC200 Printer In None
Using Barcode encoder for Font Control to generate, create Data Matrix 2d barcode image in Font applications.
www.OnBarcode.com
Copyright © OnBarcode.com . All rights reserved.