如何在文件夹中保存文件？

Question

我想在iPhone 5.1模拟器上的文档文件夹中保存数据.

 NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *filePath = [NSString stringWithFormat:@"%@/%@", documentsDirectory, @"myData.json"];

if ([[NSFileManager defaultManager] isWritableFileAtPath:filePath]) {
    NSLog(@"Writable");
}else {
    NSLog(@"Not Writable");
}

我总是"不可写".任何的想法？请帮我.

Answer 1

也许是因为您尚未创建文件,因此您测试的文件不存在.:)

你可以这样做来找到问题,

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *filePath = [NSString stringWithFormat:@"%@/%@", documentsDirectory, @"myData.json"];
NSLog(@"filePath %@", filePath);

if (![[NSFileManager defaultManager] fileExistsAtPath:filePath]) { // if file is not exist, create it.
    NSString *helloStr = @"hello world";
    NSError *error;
    [helloStr writeToFile:filePath atomically:YES encoding:NSUTF8StringEncoding error:&error];
}

if ([[NSFileManager defaultManager] isWritableFileAtPath:filePath]) {
    NSLog(@"Writable");
}else {
    NSLog(@"Not Writable");
}

Answer 2

试试这个:

NSString *data = .... // your json representation
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"myData.json"];
[data writeToFile:appFile atomically:YES encoding:NSUTF8StringEncoding error:nil];