常用的一些占位符： %@：字符串占位符 %d:整型 %ld:长整型 %f:浮点型 %c:char类型 %%：%的占位符 尽管有那么多的占位符，但是好像没有发现BOOL型的数据的占位符，这也是比较纠结的地方，看了一下别人是怎么解决这个问题的 [cpp] view plain copy print? BOOL studyBool = YES; NSLog(@"打印BOOL型数据%@",studyBool?@"YES":@"NO");//打印BOOL型数据YES NSLog(@"打印BOOL型数据%d",studyBool);//打印BOOL型数据1 BOOL alsoBool = NO; NSLog(@"打印BOOL型数据%@",alsoBool?@"YES":@"NO");//打印BOOL型数据NO NSLog(@"打印BOOL型数据%d",alsoBool);//打印BOOL型数据0 详细介绍：********************************************************** %@: Objective-C对象,印有字符串返回descriptionWithLocale:如果于的话,或描述相反.CFTypeRef工作对象,返回的结果的CFCopyDescription功能.(这个翻译有问题建议按照自己的理解方式理解)。 %%: 为'%'字符; %d,%D,%i: 为32位整型数(int); %u,%U: 为32位无符号整型数(unsigned int); %hi: 为有符号的16位整型数(short); %hu: 为无符号的16位整型数(unsigned shord); %qi: 为有符号的64位整型数(long long); %qu: 为无符号的64位整型数(unsigned long long); %x: 为32位的无符号整型数(unsigned int),打印使用数字0-9的十六进制,小写a-f; %X: 为32位的无符号整型数(unsigned int),打印使用数字0-9的十六进制,大写A-F; %qx: 为无符号64位整数(unsigned long long),打印使用数字0-9的十六进制,小写a-f; %qX: 为无符号64位整数(unsigned long long),打印使用数字0-9的十六进制,大写A-F; %o,%O: 为32位的无符号整数（unsigned int),打印八进制数; %f: 为64位的浮点数(double); %e: 为64位的浮点数(double),打印使用小写字母e,科学计数法介绍了指数的增大而减小; %E: 为64位的浮点数(double),打印科学符号使用一个大写E介绍指数的增大而减小; %g: 为64位的浮点数(double),用%e的方式打印指数,如果指数小于4或者大于等于精度,那么%f的风格就会有不同体现; %G: 为64位的浮点数(double),用%E的方式打印指数,如果指数小于4或者大于等于精度,那么%f的风格就会有不同体现; %c: 为8位的无符号字符%c(unsigned char),通过打印NSLog()将其作为一个ASCII字符,或者,不是一个ASCII字符,八进制格式ddd或统一标准的字符编码的十六进制格式udddd,在这里d是一个数字; %C: 为16位Unicode字符%C(unichar),通过打印NSLog()将其作为一个ASCII字符,或者,不是一个ASCII字符,八进制格式ddd或统一标准的字符编码的十六进制格式\udddd,在这里d是一个数字; %s: 对于无符号字符数组空终止,%s系统中解释其输入编码,而不是别的,如utf-8; %S: 空终止一系列的16位Unicode字符; %p: 空指针(无效*)，打印十六进制的数字0-9和小写a-f,前缀为0x; %L: 在明确规定的长度下,进行修正,下面的一批数据a,A,e,E,f,F,g,G应用于双精度长整型的参数; %a: 为64位的浮点数(double),按照科学计数法打印采用0x和一个十六进制数字前使用小写小数点p来介绍指数的增大而减小; %A: 为64位的浮点数(double),按照科学计数法打印采用0X和一个十六进制数字前使用大写字母小数点P界扫指数的增大而减小； %F: 为64位的浮点数(double),按照十进制表示法进行打印； %z: 修改说明在%z长度以下d,i,o,u,x,X适用于某一指定类型的转换或者适用于一定尺寸的整数类型的参数; %t: 修改说明在%t长度以下d,i,o,u,x,X适用于某一指定类型或一定尺寸的整数类型的转换的参数; %j: 修改说明在%j长度以下d,i,o,u,x,X适用于某一指定类型或一定尺寸的整数类型的转换的参数。 英文文档 格式定义 The format specifiers supported by the NSString formatting methods and CFString formatting functions follow the IEEE printf specification; the specifiers are summarized in 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 also use these format specifiers with the NSLog function. Table 1 Format specifiers supported by the NSString formatting methods and CFString formatting functions 定义 说明 %@ Objective-C object, printed as the string returned by descriptionWithLocale: if available, or description otherwise. Also works with CFTypeRef objects, returning the result of the CFCopyDescription function. %% ‘%’ 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 long long) %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 long long), printed in hexadecimal using the digits 0–9 and lowercase a–f %qX Unsigned 64-bit integer (unsigned long long), 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 or equal 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 or equal 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 the octal format \ddd or the Unicode hexadecimal format \udddd, where d is a digit %C 16-bit Unicode character (unichar), printed by NSLog() as an ASCII character, or, if not an ASCII character, in the octal format \ddd or the Unicode hexadecimal format \udddd, where d is a digit %s Null-terminated array of 8-bit unsigned characters. %s interprets its input in the system encoding rather than, for example, UTF-8. %S Null-terminated array of 16-bit Unicode characters %p Void pointer (void *), printed in hexadecimal with the digits 0–9 and lowercase a–f, with a leading 0x %L Length modifier specifying that a following a, A, e, E, f, F, g, or G conversion specifier applies to a long double argument %a 64-bit floating-point number (double), printed in scientific notation with a leading 0x and one hexadecimal digit before 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 digit before 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 a following d, i, o, u, x, or X conversion specifier applies to a size_t or the corresponding signed integer type argument %t Length modifier specifying that a following d, i, o, u, x, or X conversion specifier applies to a ptrdiff_t or the corresponding unsigned integer type argument %j Length modifier specifying that a following d, i, o, u, x, or X conversion specifier applies to a intmax_t or uintmax_t argument 平台依赖 Mac OS X uses several data types—NSInteger, NSUInteger,CGFloat, and CFIndex—to provide a consistent means of representing values in 32- and 64-bit environments. In a 32-bit environment, NSInteger and NSUInteger are defined as int and unsigned int, respectively. In 64-bit environments, NSInteger and NSUInteger are defined as long and unsigned long, respectively. To avoid the need to use different printf-style type specifiers depending on the platform, you can use the specifiers shown in Table 2. Note that in some cases you may have to cast the value. Table 2 Format specifiers for data types 类型 定义 建议 NSInteger %ld or %lx Cast the value to long NSUInteger %lu or %lx Cast the value to unsigned long CGFloat %f or %g %f works for floats and doubles when formatting; but see below warning when scanning CFIndex %ld or %lx The same as NSInteger pointer %p %p adds 0x to the beginning of the output. If you don’t want that, use %lx and cast to long. long long %lld or %llx long long is 64-bit on both 32- and 64-bit platforms unsigned long long %llu or %llx unsigned long long is 64-bit on both 32- and 64-bit platforms The following example illustrates the use of %ld to format an NSInteger and the use of a cast. NSInteger i = 42; printf("%ld ", (long)i); In addition to the considerations mentioned in Table 2, there is one extra case with scanning: you must distinguish the types for float and double. You should use %f for float, %lf for double. If you need to use scanf (or a variant thereof) with CGFloat, switch to double instead, and copy the double to CGFloat. CGFloat imageWidth; double tmp; sscanf (str, "%lf", &tmp); imageWidth = tmp; It is important to remember that %lf does not represent CGFloat correctly on either 32- or 64-bit platforms. This is unlike %ld, which works for long in all cases.