objective-c - 如何在IOS中写入文件

Question

我是IOS编程的新手。我想将一些数据写入文件。我已经成功打开了文档路径中的文件。但是fwrite不能按预期工作。如果我打开文件，则为空。它是我正在使用的代码。我做错了。

 typedef struct test {
        int a;
  } TEST_OBJ;

    TEST_OBJ test_obj1;
    test_obj1.a = 5;
    TEST_OBJ *data_ptr = &test_obj1;

    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"MyFile1.txt"];

    //This is working fine.
   // [data writeToFile:appFile atomically:YES];


    NSFileManager *fileManager = [[NSFileManager alloc]init];
    char const *path = [fileManager fileSystemRepresentationWithPath:appFile];


   FILE *fp = fopen(path, "w+b");


    // This write is not working. File is empty.
    int cnt = fwrite (data_ptr , 1 , sizeof(test_obj1) , fp );
    fclose(fp);
    fp = NULL;

有人告诉我我在做什么错吗？

Answer 1

我建议您使用 NSData 而不是C函数。

NSData *myData = [[NSData alloc] initWithBytes:bytes length:length];
[myData writeToFile:path atomically:YES];