为什么在设备上而不在模拟器上运行时会破坏数据？

Question

When running my program on a iOS simulator I didn't have a problem. But when running on my iPhone5c, I have a problem. The problem is data will be destroyed when the data was loaded. Here is my program source code. Where my code is wrong?

overview of my program:

1.load data from "sample.txt"
2.log the data

AppDelegate.h:

#import <UIKit/UIKit.h>

@interface AppDelegate : UIResponder <UIApplicationDelegate>

@property (strong, nonatomic) UIWindow *window;
@property (assign) unsigned char* bytePtr;
@property (strong, nonatomic) NSData* data;
@end

AppDelegate.m:

#import "AppDelegate.h"

@implementation AppDelegate

- (BOOL)application:(UIApplication *)application didFinishLaunchingWithOptions:(NSDictionary *)launchOptions
{
    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen] bounds]];
    // Override point for customization after application launch.
    self.window.backgroundColor = [UIColor whiteColor];
    [self.window makeKeyAndVisible];

    [self load];

    return YES;
}

- (void) load
{
    NSString* path = [[NSBundle mainBundle] pathForResource:@"sample" ofType:@"txt"];
    self.data = [NSData dataWithContentsOfFile:path];
    self.bytePtr = (unsigned char *)[self.data bytes];
    NSLog(@"%s", self.bytePtr);
}
~snip~

sample.txt:

abcdefghijklmnopqrstuvwxyz

output:

abcdefghijklmnopqrstuvwxyz
roj

expected output:

abcdefghijklmnopqrstuvwxyz

Answer 1

NSString* path = [[NSBundle mainBundle] pathForResource:@"sample" ofType:@"txt"];
self.data = [NSData dataWithContentsOfFile:path];
self.bytePtr = (unsigned char *)[self.data bytes];
NSLog(@"%s", self.bytePtr);

You're accessing data as though it is a NULL-terminated cstring (using %s ). Unless your file ends in a \\0 (which is doesn't appear to), your NSLog will just keep reading data until it finds one.

If you want to read a string from a file, using stringWithContentsOfURL:encoding:error: .