Read file in document failed in Xcode 11.3 - objective-c

Question

When I read file in document using stringWithContentsOfURL it failed
this is error in Xcode console:
Error Domain=NSCocoaErrorDomain Code=256 "The file “1.txt” couldn’t be opened." UserInfo={NSURL=/var/mobile/Containers/Data/Application/E026973D-11B6-4895-B8FE-7F9FBCC11C12/Documents/bbbb/1.txt}
this is my code:
//use objective-c
+(NSString * )loadDataFromDocumentDirectory:(NSString *)path andSubDirectory:(NSString *)subdirectory {
path = [self stripSlashIfNeeded:path];
subdirectory = [self stripSlashIfNeeded:subdirectory];
// Create generic beginning to file save path
NSMutableString *savePath = [[NSMutableString alloc] initWithFormat:#"%#/",[self applicationDocumentsDirectory].path];
[savePath appendString:subdirectory];
[savePath appendString:#"/"];
// Add requested save path
NSError *err = nil;
[savePath appendString:path];
NSURL *fileURL = [NSURL URLWithString:savePath];
NSString *loadStr = [NSString stringWithContentsOfURL:fileURL encoding:NSUTF8StringEncoding error:&err] ;
if (err) NSLog(#"load error : %#", err);
return loadStr;
}
//use swift
let loadData = FileSave.loadData(fromDocumentDirectory: "1.txt", andSubDirectory: "bbbb")

Answer 1

You are using the wrong API:
URLWithString is for URLs including the scheme (file:// or https://), for file system paths you have to use fileURLWithPath.
However it's highly recommended to use always the URL related API to build paths
+ (NSString * )loadDataFromDocumentDirectory:(NSString *)path andSubDirectory:(NSString *)subdirectory {
// path = [self stripSlashIfNeeded:path]; not needed
// subdirectory = [self stripSlashIfNeeded:subdirectory]; not needed
// Create generic beginning to file save path
NSURL *saveURL = [[self applicationDocumentsDirectory] URLByAppendingPathComponent:subdirectory];
// Add requested save path
NSError *err = nil;
NSURL *fileURL = [saveURL URLByAppendingPathComponent:path];
NSString *loadStr = [NSString stringWithContentsOfURL:fileURL encoding:NSUTF8StringEncoding error:&err] ;
if (err) NSLog(#"load error : %#", err);
return loadStr;
}