xcode 中的双重问题或我做错了什么
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double problem in xcode or me doing something wrong
提问by Tris
I would guess it's the simplest thing but it's really confusing me. I'm sure I've successfully used doubles before but now I'm having trouble.
我想这是最简单的事情，但它真的让我感到困惑。我确定我以前成功地使用过双打，但现在我遇到了麻烦。
I just made a new 'test' project to see if I can get it working, but all I'm trying to do is set a double value.
我刚刚做了一个新的“测试”项目，看看我是否可以让它工作，但我要做的就是设置一个双倍值。
So in the View Controller's viewDidLoad i've typed:
所以在视图控制器的 viewDidLoad 中，我输入了：
double z = 2938.09;
NSLog(@"z = %d", z);
I would expect it to output 'z = 2938.09' but instead I get 'z = 343597384'
我希望它输出 'z = 2938.09' 但我得到的是 'z = 343597384'
double z = 3.4 returns z = 858993459
双 z = 3.4 返回 z = 858993459
Also most integer values report back as z = 0, however not always (sometimes another strange number as above is spewed out)
此外，大多数整数值报告为 z = 0，但并非总是如此（有时会喷出另一个奇怪的数字）
Am I missing something here or it something strange going on??
我在这里遗漏了什么还是发生了一些奇怪的事情？？
Even tried stuff like
甚至尝试过类似的东西
NSString *newString = [[NSString alloc] initWithString:@"3.4"];
double z = [newString.text doubleValue];
NSLog(@"z = %d", z);
[newString release];
but still get the crazy z = 858993459 :(
但仍然疯狂 z = 858993459 :(
回答by Warrior
For printing the Double value use %f instead of %d.
要打印 Double 值，请使用 %f 而不是 %d。
NSlog format specifiers
NSlog 格式说明符
%@ Object
％@ 目的
%d, %i signed int
%d, %i 有符号整数
%u unsigned
%u 未签名
%f float/double
%f 浮点数/双倍数
%x, %X hexadecimal int
%x, %X 十六进制整数
%o octal
%o 八进制
%zu size_t
%zu size_t
%p pointer
%p 指针
%e float/double (in scientific notation)
%e 浮点数/双精度数（科学计数法）
%g float/double (as %f or %e, depending on value)
%g 浮点/双精度（如 %f 或 %e，取决于值）
%s C string (bytes)
%s C 字符串（字节）
%S C string (unichar)
%SC 字符串（单字符）
%.*s Pascal string (requires two arguments, pass pstr[0] as the first, pstr+1 as the second)
%.*s Pascal 字符串（需要两个参数，第一个传递 pstr[0]，第二个传递 pstr+1）
%c character
%c 字符
%C unichar
%C 单字符
%lld long long
%lld 长
%llu unsigned long long
%llu 无符号长长
%Lf long double
%Lf 长双
回答by vfn
Double is a double precision float, and so, to print you should use the same way used to print floats:
Double 是双精度浮点数，因此，要打印您应该使用与打印浮点数相同的方式：
NSString *newString = [[NSString alloc] initWithString:@"3.4"];
double z = [newString.text doubleValue];
NSLog(@"z = %f", z);
[newString release];
%dis used to print signed int.
%d用于打印signed int。
Have a look at this link with the format specifiers for NSLog: http://www.cocoadev.com/index.pl?NSLog
看看这个带有 NSLog 格式说明符的链接：http: //www.cocoadev.com/index.pl?NSLog
