[C ++] cstring. Format usage in MFC

In the MFCProgramUsing cstring to process strings is a good choice. Cstring can process both Unicode-standard strings and ANSI-standard strings. The format method of cstring makes it very convenient for us to convert strings. For example, to convert common numbers such as int, float, and double to a cstring, only one line is required.CodeYou can achieve this.

First, let's take a look at the format characters used for conversion:

% C single character

% D decimal INTEGER (INT)

% LD decimal INTEGER (long)

% F decimal floating point number (float)

% Lf decimal floating point number (double)

% O octal values

% S string

% U unsigned decimal number

% X hexadecimal number

1. Convert int to cstring:

Cstring STR;

Int number = 15;

// STR = "15"

Str. Format (_ T ("% d"), number );

// STR = "15" (there are two spaces in front; 4 indicates that 4 digits will be occupied. If the number exceeds 4 digits, all numbers will be output and will not be truncated)

Str. Format (_ T ("% 4D"), number );

// STR = "0015" (. 4 indicates that 4 digits will be occupied. If the number exceeds 4 digits, all numbers will be output and will not be truncated)

Str. Format (_ T ("%. 4D"), number );

The method for converting long to cstring is similar to above. You only need to change % d to % lD.

2. Convert double to cstring:

Cstring STR;

Double num = 1.46;

// STR = "1.46"

Str. Format (_ T ("% lf"), num );

// STR = "1.5" (. 1 indicates that one digit is left after the decimal point, and more than one digit is rounded off)

Str. Format (_ T ("%. 1lf"), num );

// STR = "1.4600"

Str. Format (_ T ("%. 4f"), num );

// STR = "1.4600" (there is a space in front)

Str. Format (_ T ("% 7.4f"), num );

The float conversion method to cstring is similar to the preceding method. You can change lf % to F %.

3. Convert the decimal number to octal:

Cstring STR;

Int num = 255;

// STR = "377"

Str. Format (_ T ("% O"), num );

// STR = "00000377"

Str. Format (_ T ("%. 8o"), num );

Format It is a very common but annoying method. The following is a complete overview of it for your query:

Format a string Forma ("% d", 12) It refers to a character formatted by an integer. ( I think it is to keep its shape unchanged. )
1 ). The format is always % Character , The formats of different data types are as follows: % Description after no. :
D Output signed decimal number  
O Output unsigned octal number  
X Output unsigned hexadecimal number  
U Number of output unsigned characters  
C Output Single Character  
S Output a string of characters  
F Output real number ( 6 Decimal places)  
E Output real numbers in exponential form  
G Select F And E The output format is smaller than the output width. 0
LD Input and Output Long Type data  
Lf Input and Output Double Type data  
M The data output width is M
. N Number of output decimal places N