nsfilehandle filehandleforwritingatpath:返回null!
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01-10-2019 - |
题
我的iPad应用程序有一个小的下载设施,我想使用NSFileHandle附加数据。问题是创建调用仅返回null文件处理。可能是什么问题呢?这是应该创建我的文件句柄的三行代码:
NSString *applicationDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
self.finalPath = [applicationDocumentsDirectory stringByAppendingPathComponent: self.fileName];
NSFileHandle *output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath];
我检查了文件路径,但没有发现任何错误。
泰亚
解决方案
fileHandleForWritingAtPath
不是“创建”电话。文档明确指出:“返回值:初始化的文件句柄或 零,如果路径不存在文件”(强调)。如果您想创建文件,则必须使用类似的内容:
NSFileHandle *output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath];
if(output == nil) {
[[NSFileManager defaultManager] createFileAtPath:self.finalPath contents:nil attributes:nil];
output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath];
}
如果您想将其附加到文件,如果已经存在,请使用类似的内容 [output seekToEndOfFile]
. 。然后,您的完整代码如下:
NSString *applicationDocumentsDirectory = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
self.finalPath = [applicationDocumentsDirectory stringByAppendingPathComponent: self.fileName];
NSFileHandle *output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath];
if(output == nil) {
[[NSFileManager defaultManager] createFileAtPath:self.finalPath contents:nil attributes:nil];
output = [NSFileHandle fileHandleForWritingAtPath:self.finalPath];
} else {
[output seekToEndOfFile];
}
其他提示
获取文档目录路径
+(NSURL *)getDocumentsDirectoryPath
{
return [[[NSFileManager defaultManager]URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask]lastObject];
}
将文本保存到文件的末尾
如果文件不存在,创建它并写入数据
+(void)saveText:(NSString *)textTobeSaved atPath:(NSString*)fileName
{
NSString *filePath = [NSString stringWithFormat:@"%@.text",fileName];
NSString *path = [[self getDocumentsDirectoryPath].path
stringByAppendingPathComponent:filePath];
NSFileHandle *fileHandler = [NSFileHandle fileHandleForWritingAtPath:path];
if(fileHandler == nil) {
[[NSFileManager defaultManager] createFileAtPath:path contents:nil attributes:nil];
fileHandler = [NSFileHandle fileHandleForWritingAtPath:path];
} else {
textTobeSaved = [NSString stringWithFormat:@"\n-----------------------\n %@",textTobeSaved];
[fileHandler seekToEndOfFile];
}
[fileHandler writeData:[textTobeSaved dataUsingEncoding:NSUTF8StringEncoding]];
[fileHandler closeFile];
}
从文件中获取文字 带有指定的文件名
+(NSString *)getTextFromFilePath:(NSString *)fileName
{
NSString *filePath = [NSString stringWithFormat:@"%@.text",fileName];
NSString *path = [[self getDocumentsDirectoryPath].path
stringByAppendingPathComponent:filePath];
NSLog(@"%@",path);
if(path!=nil)
{
NSString *savedString = [NSString stringWithContentsOfFile:path encoding:NSUTF8StringEncoding error:nil];
return savedString;
}else{
return @"";
}
}
删除文件
+(void)deleteFile:(NSString *)fileName
{
NSString *filePath = [NSString stringWithFormat:@"%@.text",fileName];
NSString *path = [[self getDocumentsDirectoryPath].path
stringByAppendingPathComponent:filePath];
NSFileHandle *fileHandler = [NSFileHandle fileHandleForWritingAtPath:path];
if(fileHandler != nil) {
[[NSFileManager defaultManager]removeItemAtPath:path error:nil];
}
}
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