小编Ric*_*own的帖子

我试图在Ruby中有条件地设置变量.如果变量为nil或空(0长度字符串),我需要设置它.我想出了以下内容:

variable = id if variable.nil? || (!variable.nil? && variable.empty?)

虽然它有效,但它对我来说似乎不像Ruby.表达上述内容的方式是否更为简洁？

我使用AutoMapper从平面DataObjects映射到胖BusinessObjects,反之亦然.我注意到,由于BusinessObjects的更改通知(使用自定义验证实现INotifyPropertyChanged等),从DataObjects到BusinessObjects的映射需要额外的时间.

因为我在映射期间通常不需要更改通知,所以我想将其关闭.所以我添加了一个属性"IsPropertyChangedEnabled".如果此属性设置为false,则不会引发NotifyPropertyChanged事件并保存时间.

题:

我可以告诉AutoMapper在映射过程的最开始将此属性设置为false吗？如果是这样,怎么样？

谢谢!

我创建了一个将数据字符串写入文本文件的方法.我想知道如何获得系统日期和时间并将其发送到文本文件？这是方法:

 -(void) writeToTextFile{

//get the documents dir
NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
NSString *documentsDirectory = [paths objectAtIndex:0];

//file name to write the data to using the documents directory:
NSString *fileName = [NSString stringWithFormat:@"%@/movbandlog.txt",
                      documentsDirectory];
//create content 
NSString *content = @"Data received from device\n \n \n \n \nData sent to Portal\n \n \n \n \nData received to Portal";

//save to documents directory
[content writeToFile:fileName
          atomically:NO
            encoding:NSStringEncodingConversionAllowLossy
               error:nil];

}

我正面临这个错误,在集成时opencv2.framework,任何人都可以帮助解决这个问题.我的Xcode版本是4.5.

Undefined symbols for architecture armv7:
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
      cv::Exception::Exception(int, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, int) in opencv2(system.o)
      cv::Exception::Exception(cv::Exception const&) in opencv2(system.o)
  "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::~basic_string()", referenced from:
      cv::Mat::create(int, int const*, int) in opencv2(matrix.o)
      __ZN2cvL7setSizeERNS_3MatEiPKiPKmb in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Range const&, cv::Range const&) in opencv2(matrix.o)
      cv::Mat::Mat(cv::Mat const&, cv::Range const*) in opencv2(matrix.o)
      cv::Mat::diag(int) const in opencv2(matrix.o)
      cv::Mat::Mat(_IplImage const*, bool) in opencv2(matrix.o)
      cv::Mat::reserve(unsigned …