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obj-c編程10:Foundation庫中類的使用(3)[文件管理]
好吧,不管神馬係統都無可避免的要說到文件,目錄,路徑(PATH)管理的內容,下麵我們來看看在F庫中對他們的支持.我簡單看了下,不談其他光從方法命名來說就多少顯得有點複雜,如果和ruby相比就嗬嗬了.
以下代碼功能包括文件的打開,複製,移動,取其內容,文件夾的2種遍曆方法(遞歸和非遞歸):
#import <Foundation/Foundation.h>
#define msg(...) NSLog(__VA_ARGS__)
int main(int argc, char *argv[]){
@autoreleasepool {
NSString *path = @"data.db";
NSFileManager *fm;
NSDictionary *attr;
fm = [NSFileManager defaultManager];
//check file is existed
if([fm fileExistsAtPath: path] == NO){
NSLog(@"file %@ don't exist!",path);
return 1;
}
//copy to new file ,new_file name must give
if([fm copyItemAtPath: path toPath: @"new_data.db" error:NULL] == NO){
NSLog(@"file copy failed!");
return 2;
}
//move file
if([fm moveItemAtPath:path toPath:@"fixed_data.db" error:NULL] == NO){
NSLog(@"file rename failed!");
return 3;
}
//cmp 2 file by contents
if([fm contentsEqualAtPath:@"fixed_data.db" andPath:@"new_data.db"] == NO){
NSLog(@"files are not Equal!");
}else{
NSLog(@"file are Equal!");
}
//get file size
if((attr = [fm attributesOfItemAtPath:@"fixed_data.db" error:NULL]) == nil){
NSLog(@"can't get file attr!");
}else{
msg(@"file size is %llu bytes",\
[[attr objectForKey: NSFileSize] unsignedLongLongValue]);
}
//at last we remove file
if([fm removeItemAtPath:@"new_data.db" error:NULL] == NO){
msg(@"file rm failed!");
}
}
return 0;
}
值得注意的是對於文件拷貝和移動操作,如果目標文件已存在就會失敗.而且這兩種操作都要給出目標文件名哦,切記!
對於多次操作文件內容的情況我們可以用NSData類做緩存來用,下麵是另一種文件copy操作:
#import <Foundation/Foundation.h>
#define msg(...) NSLog(__VA_ARGS__)
int main(int argc, char *argv[]){
@autoreleasepool {
NSFileManager *fm;
NSData *data;
fm = [NSFileManager defaultManager];
data = [fm contentsAtPath:@"data.db"];
if(data == nil){
NSLog(@"file read failed!");
return 1;
}
if([fm createFileAtPath:@"cp_data.db" contents:data attributes:nil] == NO){
NSLog(@"can't copy file");
return 2;
}
}
return 0;
}
對於目錄的遍曆可以使用enumeratorAtPath或者contentsOfDirectoryAtPath:error:方法(瞧著名字起的...),前者會深入遞歸子文件夾中的文件而後者不會,不過也可以動態阻止其遞歸過程,我們在下麵的代碼終將會看到如何做:
#import <Foundation/Foundation.h>
#define msg(...) NSLog(__VA_ARGS__)
int main(int argc, char *argv[]){
@autoreleasepool {
NSString *path;
NSFileManager *fm;
NSDirectoryEnumerator *dir_er;
NSArray *files;
fm = [NSFileManager defaultManager];
path = [fm currentDirectoryPath];
dir_er = [fm enumeratorAtPath:path];
msg(@"PART1 : file list in %@:",path);
while((path = [dir_er nextObject]) != nil)
msg(@"%@",path);
path = [fm currentDirectoryPath];
files = [fm contentsOfDirectoryAtPath:path error:NULL];
msg(@"PART2 : all files in path :%@",files);
BOOL flag = NO;
dir_er = [fm enumeratorAtPath:path];
msg(@"PART3 : file list in %@:",path);
while((path = [dir_er nextObject]) != nil){
msg(@"%@",path);
[fm fileExistsAtPath:path isDirectory:&flag];
if(flag == YES) [dir_er skipDescendents];
}
}
return 0;
}
注意第一次枚舉器dir_er枚舉到結尾返回後,再一次枚舉會直接返回,因為已經沒有要枚舉的對象了,我沒有找到類似於其他語言中的rewind方法,所以隻有重新給dir_er賦值鳥.運行結果如下:
wisy@wisy-ThinkPad-X61:~/src/objc_src$ ./f 2014-07-02 13:41:03.220 f[12245] PART1 : file list in /home/wisy/src/objc_src: 2014-07-02 13:41:03.222 f[12245] a 2014-07-02 13:41:03.223 f[12245] class_std 2014-07-02 13:41:03.223 f[12245] class_std/Box.m 2014-07-02 13:41:03.223 f[12245] class_std/test.m 2014-07-02 13:41:03.223 f[12245] class_std/cls_test 2014-07-02 13:41:03.223 f[12245] class_std/Box.h 2014-07-02 13:41:03.223 f[12245] class_std/cls_test.d 2014-07-02 13:41:03.223 f[12245] cp_data.db 2014-07-02 13:41:03.223 f[12245] t 2014-07-02 13:41:03.223 f[12245] dzh.m 2014-07-02 13:41:03.223 f[12245] var.m 2014-07-02 13:41:03.223 f[12245] t.d 2014-07-02 13:41:03.223 f[12245] class.m 2014-07-02 13:41:03.223 f[12245] f.m 2014-07-02 13:41:03.223 f[12245] a.d 2014-07-02 13:41:03.224 f[12245] f 2014-07-02 13:41:03.224 f[12245] normal.m 2014-07-02 13:41:03.224 f[12245] data.db 2014-07-02 13:41:03.224 f[12245] a.m 2014-07-02 13:41:03.224 f[12245] f.d 2014-07-02 13:41:03.224 f[12245] PART2 : all files in path :(a, "class_std", "cp_data.db", t, "dzh.m", "var.m", "t.d", "class.m", "f.m", "a.d", f, "normal.m", "data.db", "a.m", "f.d") 2014-07-02 13:41:03.224 f[12245] PART3 : file list in /home/wisy/src/objc_src: 2014-07-02 13:41:03.224 f[12245] a 2014-07-02 13:41:03.224 f[12245] class_std 2014-07-02 13:41:03.224 f[12245] cp_data.db 2014-07-02 13:41:03.224 f[12245] t 2014-07-02 13:41:03.224 f[12245] dzh.m 2014-07-02 13:41:03.224 f[12245] var.m 2014-07-02 13:41:03.224 f[12245] t.d 2014-07-02 13:41:03.224 f[12245] class.m 2014-07-02 13:41:03.224 f[12245] f.m 2014-07-02 13:41:03.225 f[12245] a.d 2014-07-02 13:41:03.225 f[12245] f 2014-07-02 13:41:03.225 f[12245] normal.m 2014-07-02 13:41:03.225 f[12245] data.db 2014-07-02 13:41:03.225 f[12245] a.m 2014-07-02 13:41:03.225 f[12245] f.d
待續
最後更新：2017-04-03 05:38:54