Question

大家好，我有以下java代码：

TimeZoneObj  timezone;

for( myObject obj: objectArr)
{
  if((obj.getName).equal("timeZone"))
  {
     timezone=db.getTmezone(obj.getId());
  }
}

我可以成功将其转换为lambada，如下所示：

TimeZone timezone = Arrays.stream(objectArr)
.filter(obj -> obj.getName().equals("timeZone")) //filters 
.map(obj -> db.getTmezone(obj.getId())) 
.findAny().oeElse(new TimeZoneObj);

但是如果我在主代码中有其他内容怎么办：

 TimeZoneObj  timezone;
  CalendarObj  calenda;

for( myObject obj: objectArr)
{
  if((obj.getName).equal("timeZone"))
  {
     timezone=db.getTmezone(obj.getId());
  }
  else if ((obj.getName).equal("calendar"))
  {
    calendar=db.getCalendar(obj.getId());
  }

}

任何人都可以帮我解决如何将上述代码转换为lambda的问题吗？

Answer 1

我不确定这是你想要的，但你可以用两个流来做到这一点：

Stream<myObject> timezones = Arrays.stream(objectArr).filter(obj -> obj.getName().equals("timeZone"));
Stream<myObject> calendars = Arrays.stream(objectArr).filter(obj -> obj.getName().equals("calendar"));
TimeZone timezone = timezones.map(obj -> db.getTmezone(obj.getId())).findAny().get();
CalendarObj calendar = calendars.map(obj -> db.getCalendar(obj.getId())).findAny().get();

Answer 2

在@Adi Levin的回答中回答你的问题，是的，lambda并非用于所有目的的解决方案。

话虽如此，你可以试试以下：

创建一个方法将数组元素对象映射到目标对象：

int main()
{
    string str = "NULL";
    int mappings = 0;
    readMappings(mappings);
    receiveInput(str);
    displayInput(mappings, str);
    return 0;
}
void readMappings(int &count)
{
    ifstream readMappings;                                                  // Creates the function "readMappings"
    string filename;                                                        // Generates the filename variable to search for mapping document
    cout << "Enter the filename of the mapping document: ";
    cin >> filename;                                                        // User enters filename
    readMappings.open(filename);                                            // "readMappings" function opens the given mappings document
    while (!readMappings.is_open())
    {
        cout << "Unsble to open file. Please enter a valid filename: ";     // If the user enters an invaled filename, the program will ask again
        cin >> filename;
        readMappings.open(filename);
    }   
    if (readMappings.good())                                                // Mapping document is successfully opened
    {
        readMappings >> count;                                              // Reads first line
    }
    readMappings.close();                                                   // If everything fails in this function, the document will close
}
void receiveInput(string &input)
{
    char correctness;
    do {
        cout << "\nPlease enter the text you would like to be converted to NATO:\n";
        getline(cin, input);
        cout << "You are about to convert: \"" << input << "\".\nIs this correct? (Y/N)" << endl;
        cin >> correctness;
    } while (correctness == 'N' || correctness =='n');
}

然后您可以使用它来收集您所需的对象：

    private Object fn(MyObj obj) {
        if (obj.getName().equals("timeZone")) {
            return db.getTmezone(obj.getId());
        } else if (obj.getName().equals("calendar")) {
            return db.getCalendar(obj.getId());
        } else {
            return null;
        }
    }

所以你最终的列表最多只有2个对象。但你仍然要找出对象的类型和顺序。

Answer 3

func cropImage(screenshot: UIImage) -> UIImage {
    let scale = screenshot.scale
    let imgSize = screenshot.size
    let screenHeight = UIScreen.mainScreen().bounds.height
    let bound = self.view.bounds.height
    let navHeight = self.navigationController!.navigationBar.frame.height
    let bottomBarHeight = screenHeight - navHeight - bound
    let crop = CGRectMake(0, 200, //"start" at the upper-left corner
        (imgSize.width - 1) * scale, //include half the width of the whole screen
        (imgSize.height - bottomBarHeight - 300) * scale) //include the height of the navigationBar and the height of view

    let cgImage = CGImageCreateWithImageInRect(screenshot.CGImage, crop)
    let image: UIImage = UIImage(CGImage: cgImage!)
    return image
}

我不知道。这可能不是一种不那么黑客的方式。我假设你可以......用三元运算符完成它，但唯一真实的是Adi Levin说，有两个流。

使用for循环转换代码并在有if时获取自定义对象，否则在内循环中获取

3 个答案: