怎样从沙盒里读取图片

已把图片保存，读取的时候也有路径，为什么读不到图片？
//存图片
NSData *imageData = UIImageJPEGRepresentation(currentImage, 0.5);
//获取沙盒路径
NSString *fullPath = [[NSHomeDirectory() stringByAppendingPathComponent:@"Documents"] stringByAppendingPathComponent:imageName];
[imageData writeToFile:fullPath atomically:NO];

//读取图片
NSString *fullPath = [[NSHomeDirectory() stringByAppendingPathComponent:@"Docments"] stringByAppendingPathComponent:@"currentImage.png"];
UIImage *savedImage = [[UIImage alloc] initWithContentsOfFile:fullPath];

结果savedImage是空的。