iOS中NSSearchPathForDirectoriesInDomains函數

iOS可操作目錄有兩種：Documents下與Caches下， 如圖：

1、創建目錄

createDirectoryAtPath: withIntermediateDirectories: attributes: error:
NSFileManager * fileManager = nil;
NSArray *paths = nil; 
NSString *documentsDirectory = nil;
NSString * folerName = @"Photos";
NSString * fileName = @"myphoto.png";
NSString  * filePath = nil;
UIImage *photoimage = nil;
NSData * imageData = nil;

//Documents:
paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);

//Caches:
paths = NSSearchPathForDirectoriesInDomains(NSCachesDirectory, NSUserDomainMask, YES);

documentsDirectory = [[paths objectAtIndex:0]   stringByAppendingPathComponent:folerName];

fileManager = [[NSFileManager alloc]init];
[fileManager createDirectoryAtPath:documentsDirectory withIntermediateDirectories:YES attributes:nil error:error];

2、創建目錄並在目錄中存儲對象

createFileAtPath:  contents:  attributes
filePath = [documentsDirectory stringByAppendingPathComponent:filename]; 
if((![fileManager fileExistsAtPath: fullPathToFile])) {
    photoimage = [[UIImage alloc] imageNamed:@"photo.png"];
    imageData = UIImagePNGRepresentation(photoimage);
    [fileManager createFileAtPath:filePath contents: imageData attributes:nil];
}
[photoimage release];
[fileManager release];

3、刪除目錄中指定文件

NSString * filePath = [documentsDirectory stringByAppendingPathComponent: fileName];
[filemanager removeItemAtPath: filePath error:NULL];

4、iPhone目錄

iPhone會爲每一個應用程序生成一個私有目錄，這個目錄位於：
/Users/sundfsun2009/Library/Application Support/iPhone Simulator/User/Applications下，

並隨即生成一個數字字母串作爲目錄名，在每一次應用程序啓動時，這個字母數字串都是不同於上一次。所以通常使用Documents目錄進行數據持久化的保存，而這個Documents目錄可以通過：
NSSearchPathForDirectoriesInDomains(NSDocumentDirectory,NSUserdomainMask，YES) 得到。
代碼如下：

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSLog(@"path:   %@",path);

打印結果如下：

 path:   /Users/apple/Library/Application Support/iPhone Simulator/4.3/Applications/550AF26D-174B-42E6-881B-B7499FAA32B7/Documents

而通過 NSHomeDirectory()也可以得到程序的目錄，代碼如下：

    NSString *destPath = NSHomeDirectory();
    NSLog(@"path:   %@",destPath);

打印結果如下：

    path:   /Users/apple/Library/Application Support/iPhone Simulator/4.3/Applications/550AF26D-174B-42E6-881B-B7499FAA32B7

5、返回一個絕對路徑用來存放我們需要儲存的文件。

(NSString *)dataFilePath {  
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);  
    NSString *documentsDirectory = [paths objectAtIndex:0];  
    return [documentsDirectory stringByAppendingPathComponent:@"shoppingCar.plist"];  
}  
NSFileManager* fm=[NSFileManager defaultManager];  
if(![fm fileExistsAtPath:[self dataFilePath]]){  
    //下面是對該文件進行制定路徑的保存  
    [fm createDirectoryAtPath:[self dataFilePath] withIntermediateDirectories:YES attributes:nil error:nil];  
    //取得一個目錄下得所有文件名  
    NSArray *files = [fm subpathsAtPath: [self dataFilePath] ];  
    //讀取某個文件  
    NSData *data = [fm contentsAtPath:[self dataFilePath]];  
    //或者  
    NSData *data = [NSData dataWithContentOfPath:[self dataFilePath]];  
}