"C + + GUI QT4 Programming (second Edition)"--reading experience

the Appendix D "

Getting Started with C + +

You can implement multiple classes in the same . cpp file, or you can spread the implementation of one class into multiple . cpp files

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int main (int argc, char *argv[])//argc:argument count,argv:argument value

Argv[0] The name of the depository program, argv[1],argv[2],... , Argv[argc-1] store command line arguments

Header file: Place the function prototype in a separate file, including it in all the compilation units that need to call the function.

Form:

#ifndef xxx_h #define XXX_H ... #ENDIF

#include <XXX>: angle brackets indicate that the header file XXX is located in the system's standard location

#include " XXX " : Find header file in current directory XXX

The header file is not a compilation unit, does not produce a target file, and contains only declarations that allow different compilation units to relate to each other.

Executable programs connect to many libraries

Static libraries: can be placed directly into the executable program (just like the target file)

Dynamic library: (Shared library /dll) is located in a standard location on the user's machine and is loaded automatically when the application starts

Basic data types

Instances of built-in types are not initialized by default.

Qlonglong,Qchar

the Qdatastream class is used to store platform-independent binary data

Class

Class is divided into three segments: public,protected,private without defined segments, default to Private Segment

When an inline functioncalls a function declared as an inline function, the compiler simply extends its function body and does not generate the actual function call ==>(faster)

Only very short functions should be implemented as inline functions

C + + does not provide a generic class Object that can be inherited for all classes

Pure virtual function = = "interface"

C + + does not allow the initialization of member variables in class definitions

Class variables, instance variables

Each static member variable must be defined in a . cpp file

Pointer

Heaps (heap)

Stacks (stack)

Cantilever pointer (dangling pointer) "smart" pointer:qpointer<t>

A constant pointer to a class can only be used to invoke a constant member function

"Copy on Write" in Qt (copy onwrite)

Reference

a reference in C + + stores the address of an object, unlike a pointer:

1. Disclaimer: Use "&" insteadof "*";

2. Must be initialized, cannot be re-assigned again after;

3. Direct access to the object associated with the reference;

4. Cannot be empty (null)

Array

std::memcpy () can copy a piece of data in memory

To create a variable-size array:

1. Assigning the array dynamically

2. Using the std::vector<t> class

#include <vector> std::vector<int> Array (n);

3. qvector<t> class using Qt

#include <QVector> qvector<int> Array (n);

Template classes: classes that include <> in class names

String

In C + + , the literal of a string isasimple constant character array that ends with an implicit "+" Terminator

QString

Enumeration

Sometimes enumerations are used to declare integer constants, and the name of the enumeration is usually omitted:

enum{Monday = 1; }

In other cases, enumerations are used to express the collection of options, with an enumeration constant that is the value of a power of 2 to represent the individual selections , each of which is oftenreferred to as "flag", and the bitwise operator can be used | "or" |= to combine these tags, you can use the bitwise operator & totest whether a tag is selected.

Type aliases

Type conversions

Static_cast<t> () converts a pointer to a pointer to b , class b must be a class A sub-class

Dynamic_cast<t> () run-time type information (RTTI,runtime type information) validation

Const_cast<t> () add / Remove a const qualifier on a pointer or reference

Reinterpret_cast<t> () converts any type of pointer or reference to any other type

Data type VOID * can store address of any type of instance

Keyword explicit to disable the auto-transform feature

Operator overloading

Value type

Value type, reference type (referencetype)

all types in C + + can be used as reference types

If you want to have a C + + class has a replicable nature, you must ensure that the class has a complex constructor ( copy Constructor ) and an assignment operator. When you define a class, the C + + compiler automatically provides a copy constructor and an assignment operator to perform member-to-member replication.

Global variables and global functions

Not to be continued ....

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"C + + GUI QT4 Programming (second Edition)"--reading experience