NSlog警告—— 编译器打印NSInteger类型
NSInter是apple推荐用的整形数据类型，在mac64位环境下用打印NSInteger的时候如果用%d，编译器会报警告:
对于32位代码，需要的%d说明符。但是，如果%d说明，得到的64位提示警告用%ld代替：
而如果%ld相匹配的64位大小，32位代码中，会得到一个警告提示%d代替：
如何解决呢？
NSInteger的定义是这样的 :
#if __LP64__ || (TARGET_OS_EMBEDDED && !TARGET_OS_IPHONE) || TARGET_OS_WIN32 || NS_BUILD_32_LIKE_64
typedef long NSInteger;
typedef unsigned long NSUInteger;
#else
typedef int NSInteger;
typedef unsigned int NSUInteger;
#endif
也就是说64位下是long 类型，十六进制， 32位下是int类型， 8进制；
我的解决方法：
用%i 或者 %zi代替， %zi 是非负整数；
原因：
%i和%d都是表示有符号十进制整数，但%i可以自动将输入的八进制（或者十六进制）转换为十进制，而%d则不会进行转换。
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 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.
| 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.
| 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.
|
1
2 |
NSInteger i = 42;
printf("%ld\n", (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.
|
1
2 3 4 |
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.
其他的补充：
%@ 对象
%d, %i 整数
%u 无符整形
%f 浮点/双字
%x, %X 二进制整数
%o 八进制整数
%zu size_t
%p 指针
%e 浮点/双字 （科学计算）
%g 浮点/双字
%s C 字符串
%.*s Pascal字符串
%c 字符
%C unichar
%lld 64位长整数（long long）
%llu 无符64位长整数
%Lf 64位双字
