Turn: char*, char[], CString, string conversion

turn: char*, char[], CString, string conversion

(i) Overview

String and CString are string template classes, string classes defined by the Standard template class (STL), are included in the C + + standard;

CString (typedef CStringT > CString) is the most commonly used string class in Visual C + + and inherits from the CSimpleStringT class, mainly used in MFC and ATL programming, with char (applied to ANSI) for main data types , wchar_t (Unicode), TCHAR (ANSI and Unicode are available);

Char* is the most commonly used string pointer in C programming, usually with "' as the end flag;

(ii) Construction

The string is convenient and can be constructed from almost all strings, including CString and char*;

CString second, can be constructed from some basic string variables, including char* and so on;

Char* does not have a constructor, only can be assigned value;

Example:

char* psz = "Joise";

CString CStr (PSZ);

String str (CSTR);

(c) operator overloading

A) operator=

String is the most convenient and can be used to assign values to almost all strings, including CString and char*;

CString second, can directly use some basic string assignment, including char* and so on;

Char* can only be assigned by pointers, and is extremely dangerous operation, it is recommended to use strcpy or memcpy, and char* at the time of declaration, if the initial value is not assigned to the proposed first set to NULL, to avoid wild pointers, so you are crazy;

Example:

char *psz = NULL;

Psz = new CHAR[10]; Of course, the above is directly written as char *psz = new CHAR[10];

memset (psz, 0, 10);

strcpy (Psz, "joise");

CString CStr;

CStr = Psz;

String str;

str = PSZ;

str = CStr;

delete []psz;

b) operator+

String is similar to CString, can be directly with the char* to add, but can not use the + operator, that is, string str = str + CSTR is illegal, must be converted to char*;

Char* does not have a + operation, can only use strcat to connect two pointers together;

Example:

char* psz = "Joise";

CString CStr = psz;

CStr = CStr + psz;

string str = Psz;

str = str + str + psz;

strcat (Psz, psz);

strcat (Psz, CStr);//Legal

strcat (Psz, str);//Illegal, this shows that CString can be automatically converted to a const char*, and string does not

c) operator + =

String is the most powerful and can be used with all string variables + =, including CString and char*;

CString second, can be compared with some basic string variables + =, including char*, etc.;

Char* does not have the + = operator and can only use strcat to connect two pointers together;

d) operator[]

CString is best when an assertion exception is thrown when crossing the bounds;

String and char* subscript out-of-bounds results not defined;

Example:

char* psz = "Joise";

CString CStr = psz;

cout << cstr[8];

string str = Psz;

cout << str[8];

cout << psz[8];

e) operator==, operator!=, operator>, operator<, operator>=, perator<=

CString and string can not be compared, but can be compared with char*, and the comparison is the value, not the address;

cout << (Psz = = CStr);

cout << (psz = = str);

cout << (str = = Psz);

cout << (CStr = = psz);//The above code return is 1

(iv) common algorithms

A) Find

Role	char*	String	CString
Find specified value	Strchr Strstr Strrstr Strspn	Find	Find
The first matching value		Fild_first_of	Findoneof
Find from the back			Reservefind
Specify the matching method		Find_if

Note: In find_if, the values in the range are put into the matching function until True

b) Comparison

Role	char*	String	CString
Find specified value (case sensitive)	strcmp strncmp Strcoll _strncoll	operator< Operator> operator<= operator>= operator== operator!=	Collate Compare
Find specified value (case insensitive)	_stricmp _strnicmp _stricoll _strnicoll		Collatenocase Comparenocas

Note: The return value if <0 is lower than the value that follows, and vice versa

c) Replace

Role	char*	String	CString
Find specified value	_strset _strnset	Replace Replace_copy Replace_copy_if Replace_if	Replace

d) Insert

Role	char*	String	CString
Find specified value		Insert	Insert

e) Increase

Role	char*	String	CString
Dynamic add Value	Strcat	Push Append	Append Appendchar AppendFormat

f) Interception

Role	char*	String	CString
Get partial value	Use subscript operation	Substr	Left Mid Right Truncate

g) Remove

Role	char*	String	CString
Remove partial values		Remove	Remove
To remove a blank value	Removeblanks Note: This is provided for ATL, non-C functions	Remove_if	Trim Trimleft Trimrig

h) Convert case

Role	char*	String	CString
Convert case	_strlwr _strupr		Makelower Makeupper

i) and other types of conversions

Role	char*	String	CString
Convert to Digital	Atoi Atod Atof		Format
Convert to Char*		C_str	GetBuffer Getbuffersetlen

j) Formatting

Role	char*	String	CString
Formatting	sprintf		Format

k) Get length

Role	char*	String	CString
Get the length	Strlen	Length	GetLength
Get size		Size	Getalloclength

L) judged to be empty

Role	char*	String	CString
Determines whether the empty	Determine if ==null or whether the first character is '	Empty	IsEmpty

m) Redefine size

Role	char*	String	CString
Redefine size	ReAlloc New	Resize	GetBufferSetLength

N) Releasing Resources

Role	char*	String	CString
Release	Free Delete (delete[])		ReleaseBuffer Releasebuffersetlength

(v) Safety >

CString > String > char*;

(vi) Flexibility

CString > String >char*;

(vii) Portability

char* = string > CString

(eight) implementation of the conversion            

1.string Turn CString
Cstring.format ("%s", String.c_str ());

2.char Turn CString
Cstring.format ("%s", char*);

3.char to String
string S (char *);

4.string Turn char *
Char *p = STRING.C_STR ();

5.CString Turn string
String s (Cstring.getbuffer ());

6.string-CString
Cstring.format ("%s", String.c_str ());
Using C_str () is really better than data ().
7.CString, String
String s (Cstring.getbuffer ());
GetBuffer () must be releasebuffer (), otherwise the space occupied by the buffer will not be released.
8. There are three functions to convert the contents of a string to a character array and c-string
1.data (), returns a string array without ""
2,C_STR (), returns a string array with ""
3,copy ()

9. Convert characters to integers, you can use Atoi, _atoi64, or ATOL.
10. Convert a number to a CString variable, you can use the CString format function

CString s;
int i = 64;
S.format ("%d", i)
The Format function is very powerful and deserves your research.

11.cstring to char *
Charpoint=strtest. GetBuffer (strtest. GetLength ());

12.CString conversion char[100]

Char a[100];
CString Str ("aaaaaa");
strncpy (A, (LPCTSTR) str,sizeof (a));

Turn: char*, char[], CString, string conversion