1.字符串格式化
Nsstring *p =@"an apple";
NSLog(@"whatis this? it is %@",p);
Objective-C中的字符串格式化输出
在使用诸如NSLog,[Nsstring stringWithFormat:]之类的函数时,都是基于c/c++风格的字符串格式化工作的.本来c/c++就没怎么用过,到iphone开发开发
转自http://blog.kungfusoft.com/programming/iphone/topic-281.html
在使用诸如NSLog,都是基于c/c++风格的字符串格式化工作的.
本来c/c++就没怎么用过,到iphone开发开发时掺合上NS系的对象,格式化输出更是一头的乱.
看了一下Programming Guide for Cocoa的文档,还是有比较详尽的说明的,整理出来备查.
格式定义
The formatspecifiers supported by the Nsstring formatting methods and CFString formattingfunctions follow the IEEE printf specification; the specifiers are summarizedin Table 1. Note that you can also use the “n$” positional specifiers such as%1$@ %2$s. For more details,see the IEEE printf specification. You can alsouse these format specifiers with the NSLog function.
Table 1 Formatspecifiers supported by the Nsstring formatting methods and CFString formattingfunctions 定义 说明
%@ Objective-C object,printed as the stringreturned by descriptionWithLocale: if available,or description otherwise. Alsoworks with CFTypeRef objects,returning the result of the CFcopyDescriptionfunction.
%% ‘%’ character
%d,%D,%i Signed 32-bit integer (int)
%u,%U Unsigned 32-bit integer (unsigned int)
%hi Signed 16-bit integer (short)
%hu Unsigned 16-bit integer (unsigned short)
%qi Signed 64-bit integer (long long)
%qu Unsigned 64-bit integer (unsigned longlong)
%x Unsigned 32-bit integer (unsigned int),printed in hexadecimal using the digits 0–9 and lowercase a–f
%X Unsigned 32-bit integer (unsigned int),printed in hexadecimal using the digits 0–9 and uppercase A–F
%qx Unsigned 64-bit integer (unsigned longlong),printed in hexadecimal using the digits 0–9 and lowercase a–f
%qX Unsigned 64-bit integer (unsigned longlong),printed in hexadecimal using the digits 0–9 and uppercase A–F
%o,%O Unsigned 32-bit integer (unsigned int),printed in octal
%f 64-bit floating-point number (double)
%e 64-bit floating-point number (double),printed in scientific notation using a lowercase e to introduce the exponent
%E 64-bit floating-point number (double),printed in scientific notation using an uppercase E to introduce the exponent
%g 64-bit floating-point number (double),printed in the style of %e if the exponent is less than –4 or greater than orequal to the precision,in the style of %f otherwise
%G 64-bit floating-point number (double),printed in the style of %E if the exponent is less than –4 or greater than orequal to the precision,in the style of %f otherwise
%c 8-bit unsigned character (unsigned char),printed by NSLog() as an ASCII character,or,if not an ASCII character,in theoctal format \\ddd or the Unicode hexadecimal format \\udddd,where d is adigit
%C 16-bit Unicode character (unichar),where d is adigit
%s Null-terminated array of 8-bit unsignedcharacters. %s interprets its input in the system encoding rather than,forexample,UTF-8.
%s Null-terminated array of 16-bit Unicodecharacters
%p Void pointer (void *),printed inhexadecimal with the digits 0–9 and lowercase a–f,with a leading 0x
%L Length modifier specifying that afollowing a,A,e,E,f,F,g,or G conversion specifier applies to a longdouble argument
%a 64-bit floating-point number (double),printed in scientific notation with a leading 0x and one hexadecimal digitbefore the decimal point using a lowercase p to introduce the exponent
%A 64-bit floating-point number (double),printed in scientific notation with a leading 0X and one hexadecimal digitbefore the decimal point using a uppercase P to introduce the exponent
%F 64-bit floating-point number (double),printed in decimal notation
%z Length modifier specifying that afollowing d,i,o,u,x,or X conversion specifier applies to a size_t or thecorresponding signed integer type argument
%t Length modifier specifying that a following d,or X conversion specifier applies to a ptrdiff_t or thecorresponding unsigned integer type argument
%j Length modifier specifying that a following d,or X conversion specifier applies to a intmax_t or uintmax_targument
平台依赖
Mac OS X usesseveral data types—NSInteger,NSUInteger,CGFloat,and CFIndex—to provide aconsistent means of representing values in 32- and 64-bit environments. In a32-bit environment,NSInteger and NSUInteger are defined as int and unsignedint,respectively. In 64-bit environments,NSInteger and NSUInteger are definedas long and unsigned long,respectively. To avoid the need to use differentprintf-style type specifiers depending on the platform,you can use thespecifiers shown in Table 2. Note that in some cases you may have to cast thevalue.
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