NSSearchPathForDirectoriesInDomains解释混淆 [英] NSSearchPathForDirectoriesInDomains explanation confused

问题描述

我刚才一直在研究这个code，它检查文件是否存在：

 的NSString *路径;
NSArray的*路径= NSSearchPathForDirectoriesInDomains（NSDocumentDirectory，NSUserDomainMask，YES）;
路径= [[路径objectAtIndex：0] stringByAppendingPathComponent：@SomeDirectory];
路径= [路径stringByAppendingPathComponent：@SomeFileName];
如果（[的NSFileManager defaultManager] fileExistsAtPath：路径]）
{
 

但我有点困惑。通过以下行：

 的NSArray *路径= NSSearchPathForDirectoriesInDomains（NSDocumentDirectory，NSUserDomainMask，YES）;
 

好吧，我明白的方法NSSearchPathForDirectoriesInDomains返回，这取决于你传递到该方法的参数的路径。但这个用户（谁写的code）是一味传递一个全班同学！ （指的是NSDocumentDirectory，NSUserDOmainMask）。他正确地传递的唯一一件事就是BOOL YES。我检查了苹果的文档，它说的：

NSSearchPathForDirectoriesInDomains创建的目录搜索路径列表。

 的NSArray * NSSearchPathForDirectoriesInDomains（
NSSearchPathDirectory目录，
NSSearchPathDomainMask domainMask，
BOOL expandTilde
）;
 

我在苹果的文档搜索NSSearchPathDirectory和NSSearchPathDomainMask他们建议我一定要通过一些

这表明需要传递到方法是多少？有人能解释一下行吗？谢谢

解决方案

在这里Foundation框架常量阅读文档：结果
<一href=\"http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_DataTypes/Reference/reference.html#//apple_ref/doc/c_ref/NSDocumentDirectory\">http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_DataTypes/Reference/reference.html#//apple_ref/doc/c_ref/NSDocumentDirectory

这是正确的使用，因为这些都不是类，但常量！

---

NSSearchPathDomainMask

  

搜索路径域指定常量为NSSearchPathDirectory式底座的位置。

  {枚举
   NSUserDomainMask = 1，//这一个
   NSLocalDomainMask = 2，
   NSNetworkDomainMask = 4，
   NSSystemDomainMask = 8，
   NSAllDomainsMask = 0x0ffff，
};
的typedef NSUInteger NSSearchPathDomainMask;
 

---

NSSearchPathDirectory

  

这些常量指定各种目录的位置。

  {枚举
   NSApplicationDirectory = 1，
   NSDemoApplicationDirectory，
   NSDeveloperApplicationDirectory，
   NSAdminApplicationDirectory，
   NSLibraryDirectory，
   NSDeveloperDirectory，
   NSUserDirectory，
   NSDocumentationDirectory，
   NSDocumentDirectory，//这一个
   NSCoreServiceDirectory，
   NSAutosavedInformationDirectory = 11，
   NSDesktopDirectory = 12，
   NSCachesDirectory = 13，
   NSApplicationSupportDirectory = 14，
   NSDownloadsDirectory = 15，
   NSInputMethodsDirectory = 16，
   NSMoviesDirectory = 17，
   NSMusicDirectory = 18，
   NSPicturesDirectory = 19，
   NSPrinterDescriptionDirectory = 20，
   NSSharedPublicDirectory = 21，
   NS preferencePanesDirectory = 22，
   NSItemReplacementDirectory = 99，
   NSAllApplicationsDirectory = 100，
   NSAllLibrariesDirectory = 101
};
的typedef NSUInteger NSSearchPathDirectory;
 

I have just been studying this code which checks if a file exists:

NSString *path;
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
path = [[paths objectAtIndex:0] stringByAppendingPathComponent:@"SomeDirectory"];
path = [path stringByAppendingPathComponent:@"SomeFileName"];
if ([[NSFileManager defaultManager] fileExistsAtPath:path])
{

but I'm a bit confused. by the following line:

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserDomainMask, YES);

Ok I Understand that the Method NSSearchPathForDirectoriesInDomains returns a path depending on the arguments which you pass into this method. But this user (whoever wrote the code) is blindly passing in a whole class! (refering to NSDocumentDirectory, NSUserDOmainMask). The only thing he pass correctly is the BOOL YES. I check the apple docs and it says this:

NSSearchPathForDirectoriesInDomains Creates a list of directory search paths.

NSArray * NSSearchPathForDirectoriesInDomains (
NSSearchPathDirectory directory,
NSSearchPathDomainMask domainMask,
BOOL expandTilde
);

I have search for NSSearchPathDirectory and NSSearchPathDomainMask in apple docs and they suggest I have to pass a number

This would suggest a number needs to be passed into the method? Can somebody explain that line please? thanks

解决方案

Read documentation of Foundation framework constants here:
http://developer.apple.com/library/mac/#documentation/Cocoa/Reference/Foundation/Miscellaneous/Foundation_DataTypes/Reference/reference.html#//apple_ref/doc/c_ref/NSDocumentDirectory

It's correct usage, because those are not classes but constants!

---

NSSearchPathDomainMask

Search path domain constants specifying base locations for the NSSearchPathDirectory type.

enum {
   NSUserDomainMask = 1, //this one
   NSLocalDomainMask = 2,
   NSNetworkDomainMask = 4,
   NSSystemDomainMask = 8,
   NSAllDomainsMask = 0x0ffff,
};
typedef NSUInteger NSSearchPathDomainMask;

---

NSSearchPathDirectory

These constants specify the location of a variety of directories.

enum {
   NSApplicationDirectory = 1,
   NSDemoApplicationDirectory,
   NSDeveloperApplicationDirectory,
   NSAdminApplicationDirectory,
   NSLibraryDirectory,
   NSDeveloperDirectory,
   NSUserDirectory,
   NSDocumentationDirectory,
   NSDocumentDirectory,  // this one
   NSCoreServiceDirectory,
   NSAutosavedInformationDirectory = 11,
   NSDesktopDirectory = 12,
   NSCachesDirectory = 13,
   NSApplicationSupportDirectory = 14,
   NSDownloadsDirectory = 15,
   NSInputMethodsDirectory = 16,
   NSMoviesDirectory = 17,
   NSMusicDirectory = 18,
   NSPicturesDirectory = 19,
   NSPrinterDescriptionDirectory = 20,
   NSSharedPublicDirectory = 21,
   NSPreferencePanesDirectory = 22,
   NSItemReplacementDirectory = 99,
   NSAllApplicationsDirectory = 100,
   NSAllLibrariesDirectory = 101
};
typedef NSUInteger NSSearchPathDirectory;

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