Objective-c中的佔位符,列印BOOL型別資料
常用的一些佔位符:
%@:字串佔位符
%d:整型
%ld:長整型
%f:浮點型
%c:char型別
%%:%的佔位符
儘管有那麼多的佔位符,但是好像沒有發現BOOL型的資料的佔位符,這也是比較糾結的地方,看了一下別人是怎麼解決這個問題的
[cpp] view plaincopyprint?- BOOL studyBool = YES;
- NSLog(@"列印BOOL型資料%@",[email protected]"YES":@"NO");//列印BOOL型資料YES
-
NSLog(@"列印BOOL型資料%d",studyBool);
- BOOL alsoBool = NO;
- NSLog(@"列印BOOL型資料%@",[email protected]"YES":@"NO");//列印BOOL型資料NO
- NSLog(@"列印BOOL型資料%d",alsoBool);//列印BOOL型資料0
詳細介紹:**********************************************************
%@: Objective-C物件,印有字串返回descriptionWithLocale:如果於的話,或描述相反.CFTypeRef工作物件,返回的結果的CFCopyDescription功能.(這個翻譯有問題建議按照自己的理解方式理解)。
%%: 為'%'字元;
%d,%D,%i: 為32位整型數(int);
%u,%U: 為32位無符號整型數(unsigned int);
%hi: 為有符號的16位整型數(short);
%hu: 為無符號的16位整型數(unsigned shord);
%qi: 為有符號的64位整型數(long long);
%qu: 為無符號的64位整型數(unsigned long long);
%x: 為32位的無符號整型數(unsigned int),列印使用數字0-9的十六進位制,小寫a-f;
%X: 為32位的無符號整型數(unsigned int),列印使用數字0-9的十六進位制,大寫A-F;
%qx: 為無符號64位整數(unsigned long long),列印使用數字0-9的十六進位制,小寫a-f;
%qX: 為無符號64位整數(unsigned long long),列印使用數字0-9的十六進位制,大寫A-F;
%o,%O: 為32位的無符號整數(unsigned int),列印八進位制數;
%f: 為64位的浮點數(double);
%e: 為64位的浮點數(double),列印使用小寫字母e,科學計數法介紹了指數的增大而減小;
%E: 為64位的浮點數(double),列印科學符號使用一個大寫E介紹指數的增大而減小;
%g: 為64位的浮點數(double),用%e的方式列印指數,如果指數小於4或者大於等於精度,那麼%f的風格就會有不同體現;
%G: 為64位的浮點數(double),用%E的方式列印指數,如果指數小於4或者大於等於精度,那麼%f的風格就會有不同體現;
%c: 為8位的無符號字元%c(unsigned char),通過列印NSLog()將其作為一個ASCII字元,或者,不是一個ASCII字元,八進位制格式\ddd或統一標準的字元編碼的十六進位制格式\udddd,在這裡d是一個數字;
%C: 為16位Unicode字元%C(unichar),通過列印NSLog()將其作為一個ASCII字元,或者,不是一個ASCII字元,八進位制格式\ddd或統一標準的字元編碼的十六進位制格式\\udddd,在這裡d是一個數字;
%s: 對於無符號字元陣列空終止,%s系統中解釋其輸入編碼,而不是別的,如utf-8;
%S: 空終止一系列的16位Unicode字元;
%p: 空指標(無效*),列印十六進位制的數字0-9和小寫a-f,字首為0x;
%L: 在明確規定的長度下,進行修正,下面的一批資料a,A,e,E,f,F,g,G應用於雙精度長整型的引數;
%a: 為64位的浮點數(double),按照科學計數法列印採用0x和一個十六進位制數字前使用小寫小數點p來介紹指數的增大而減小;
%A: 為64位的浮點數(double),按照科學計數法列印採用0X和一個十六進位制數字前使用大寫字母小數點P界掃指數的增大而減小;
%F: 為64位的浮點數(double),按照十進位制表示法進行列印;
%z: 修改說明在%z長度以下d,i,o,u,x,X適用於某一指定型別的轉換或者適用於一定尺寸的整數型別的引數;
%t: 修改說明在%t長度以下d,i,o,u,x,X適用於某一指定型別或一定尺寸的整數型別的轉換的引數;
%j: 修改說明在%j長度以下d,i,o,u,x,X適用於某一指定型別或一定尺寸的整數型別的轉換的引數。
英文文件
格式定義
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$” positional specifiers such as %[email protected] %2$s.
For more details, see the IEEE printf specification. You can also use these format specifiers with the NSLog function.
定義 | 說明 |
%@ | 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 |
平臺依賴
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.
型別 | 定義 | 建議 |
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.