如何正确获取文件大小，并将其转换为MB，GB在Cocoa？ [英] How to get file size properly and convert it to MB, GB in Cocoa?

问题描述

可能重复：

ObjC / Cocoa类将大小转换为人类可读的字符串？

我是Cocoa的新人。我正在尝试正确获取文件夹文件的大小。如果它少于1 GB或以GB为单位，则以MB为单位显示。

我想显示的方式在点后四舍五入。

示例
5.5 MB （如果超过1000） 1.1 GB

我尝试使用此

  unsigned long long size =（[[[NSFileManager defaultManager] attributesOfItemAtPath：fullPath error：nil] fileSize]）; 
  

但我不能正确转换数字，并显示它， p>

感谢。

解决方案

函数

   - （id）transformedValue：（id）value 
 {
 
 double convertedValue = [value doubleValue]; 
 int multiplyFactor = 0; 
 
 NSArray * tokens = [NSArray arrayWithObjects：@bytes，@KB，@MB，@GB，@TB，@PB ，ZB，YB，nil]; 
 
 while（convertedValue> 1024）{
 convertedValue / = 1024; 
 multiplyFactor ++; 
} 
 
 return [NSString stringWithFormat：@％4.2f％@，convertedValue，[tokens objectAtIndex：multiplyFactor]]; 
} 
  

编辑：

您还可以使用 NSByteCountFormatter 类。

  [NSByteCountFormatter stringFromByteCount：1999 countStyle：NSByteCountFormatterCountStyleFile];可在iOS 6.0 / OS X v10.8及更高版本中使用。 
  

您可以使用 NSByteCountFormatterCountStyleFile ， NSByteCountFormatterCountStyleMemory ， NSByteCountFormatterCountStyleDecimal 或 NSByteCountFormatterCountStyleBinary in countStyle。

NSByteCountFormatterCountStyleFile ：指定文件或存储字节计数的显示。这个的实际行为是
平台特定;在OS X 10.8，这使用十进制风格，但
可能会随时间而变化。

NSByteCountFormatterCountStyleMemory ：指定显示内存字节计数。它的实际行为是平台特定的;在OS
X 10.8，这使用二进制风格，但可能会随时间更改。

NSByteCountFormatterCountStyleDecimal ：明确指定KB的字节数，1000字节显示为1 KB

NSByteCountFormatterCountStyleBinary ：明确指定KB的字节数，1024字节显示为1 KB

现代的Objective-c syntext：

   - （id）transformedValue：（id）value 
 {
 
 double convertedValue = [value doubleValue]; 
 int multiplyFactor = 0; 
 
 NSArray * tokens = @ [@bytes，@KB，@MB，@GB，@TB，@PB，@EB ZB，YB]; 
 
 while（convertedValue> 1024）{
 convertedValue / = 1024; 
 multiplyFactor ++; 
} 
 
 return [NSString stringWithFormat：@％4.2f％@，convertedValue，tokens [multiplyFactor]]; 
} 
  

Possible Duplicate:
ObjC/Cocoa class for converting size to human-readable string?

I'm new in Cocoa. I'm trying to get size of folder files properly. And display it in MB if it less 1 GB , or in GB.

The way I want it to display is rounded with one number after point.

Example 5.5 MB if it is more than 1000 > 1.1 GB

I'm trying to use this

 unsigned  long long size= ([[[NSFileManager defaultManager] attributesOfItemAtPath:fullPath error:nil] fileSize]);

But I can't a way properly convert number, and display it , as I want.

Thanks.

解决方案

For converting file size to MB, Gb use below function

- (id)transformedValue:(id)value
{

    double convertedValue = [value doubleValue];
    int multiplyFactor = 0;

    NSArray *tokens = [NSArray arrayWithObjects:@"bytes",@"KB",@"MB",@"GB",@"TB",@"PB", @"EB", @"ZB", @"YB",nil];

    while (convertedValue > 1024) {
        convertedValue /= 1024;
        multiplyFactor++;
    }

    return [NSString stringWithFormat:@"%4.2f %@",convertedValue, [tokens objectAtIndex:multiplyFactor]];
}

EDIT:

You can also use NSByteCountFormatter class. Available in iOS 6.0 / OS X v10.8 and later.

[NSByteCountFormatter stringFromByteCount:1999 countStyle:NSByteCountFormatterCountStyleFile];

You can use NSByteCountFormatterCountStyleFile, NSByteCountFormatterCountStyleMemory, NSByteCountFormatterCountStyleDecimal or NSByteCountFormatterCountStyleBinary in countStyle.

NSByteCountFormatterCountStyleFile: Specifies display of file or storage byte counts. The actual behavior for this is platform-specific; on OS X 10.8, this uses the decimal style, but that may change over time.

NSByteCountFormatterCountStyleMemory: Specifies display of memory byte counts. The actual behavior for this is platform-specific; on OS X 10.8, this uses the binary style, but that may change over time.

NSByteCountFormatterCountStyleDecimal: Specifies the number of bytes for KB explicitly, 1000 bytes are shown as 1 KB

NSByteCountFormatterCountStyleBinary: Specifies the number of bytes for KB explicitly, 1024 bytes are shown as 1 KB

Modern Objective-c syntext:

- (id)transformedValue:(id)value
{

    double convertedValue = [value doubleValue];
    int multiplyFactor = 0;

    NSArray *tokens = @[@"bytes",@"KB",@"MB",@"GB",@"TB",@"PB", @"EB", @"ZB", @"YB"];

    while (convertedValue > 1024) {
        convertedValue /= 1024;
        multiplyFactor++;
    }

    return [NSString stringWithFormat:@"%4.2f %@",convertedValue, tokens[multiplyFactor]];
}

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