英文:
Scala Type Mismatch, Can't Resolve the Problem
问题
为了项目中的一个部分，我试图让游戏生成的方块移动。所有坐标都存储在一个列表中，通过 "x" 和 "y" 值，我应该能够累加到坐标上，从而使方块移动。
def movement(move: Point): Unit = {val newList: List[Point] = placedval xx = move.x; val yy = move.yfor (i <- newList.indices) newList(i) += Point(xx, yy)}
在这里，"placed" 是存放所有坐标的列表。"Point" 类型是指 "x" 和 "y" 值。
问题在于，当我尝试将新值添加到坐标时，它会显示：
> 类型不匹配。需要：字符串，找到：Point
我觉得这很奇怪，因为我的列表不是以字符串类型初始化的。有没有解决这个问题的方法？
非常感谢。
添加了先前项目的示例：
var playAnimal: List[Point] = List(Point(2,0), Point(1,0), Point(0,0))def checkForWrap(p: Point): Point = {var x = p.x; var y = p.yx = if (x < 0) nrColumns - 1 else if (x > nrColumns - 1) 0 else xy = if (y < 0) nrRows - 1 else if (y > nrRows - 1) 0 else yPoint(x, y)}def moveAnimal(): Unit = {if (!gameOver) {def newAnimalFront: Point = {val newHead: Point = currentDir match {case East() => playAnimal.head + Point(1, 0)case West() => playAnimal.head + Point(-1, 0)case North() => playAnimal.head + Point(0, -1)case South() => playAnimal.head + Point(0, 1)}checkForWrap(newHead)}playAnimal = newAnimalFront +: playAnimal.init}}
然而，在我的当前项目中，这种方法显示了字符串不匹配的错误。
英文:
So, for a project, I'm trying to make a specific piece of a game generated block move. All coordinates are stored in a List and through "x" and "y" values I should be able to add up to the coordinates, and in turn make the block move.
def movement(move: Point): Unit = {val newList: List[Point] = placedval xx = move.x; val yy = move.yfor (i <- newList.indices) newList(i) += Point(xx, yy)}
Here, "placed" is the List where all coordinates are placed. The "Point" type refers to the "x" and "y" values.
The problem here is that when I try to add the new values to the coordinate, it says:
> Type mismatch. Required: String, found: Point
I found this strange, since my list is not initiated with the string type. Is there any way to work around this problem?
Many thanks.
Added example of previous project:
var playAnimal: List[Point] = List(Point(2,0), Point(1,0), Point(0,0))def checkForWrap (p: Point) : Point = {var x = p.x; var y = p.yx = if (x < 0) nrColumns - 1 else if (x > nrColumns - 1) 0 else xy = if (y < 0) nrRows - 1 else if (y > nrRows - 1) 0 else yPoint(x, y)}def moveAnimal(): Unit = {if(!gameOver) {def newAnimalFront: Point = {val newHead: Point = currentDir match {case East() => playAnimal.head + Point( 1, 0)case West() => playAnimal.head + Point(-1, 0)case North() => playAnimal.head + Point( 0, -1)case South() => playAnimal.head + Point( 0, 1)}checkForWrap(newHead)}playAnimal = newAnimalFront +: playAnimal.init}}
This method, however, is displaying the String mismatch in my current project.
答案1
得分: 1
两件事情你需要做：
- 在你的类
Point中定义方法+。 - 避免变异（这取决于你，但你的代码会更易读）。
然后你可以编写类似这样的代码：
def main(args: Array[String]): Unit = {val placed: List[Point] = List(Point(0, 0), Point(1, 1))println(placed.mkString) // Point(0,0)Point(1,1)val moved = movement(Point(2, 2), placed)println(moved.mkString) //Point(2,2)Point(3,3)}def movement(move: Point, placed: List[Point]): List[Point] = {// 这里你创建了一个新的列表，没有改变旧的列表placed.map(p => p + move)}case class Point(x: Int, y: Int) {def +(p: Point) = Point(x + p.x, y + p.y)}
英文:
Two things you need to do:
- Define in your class
Pointmethod+. - Avoid mutations(it's up to you but your code becomes more readable).
Then you can write smth like this:
def main(args: Array[String]): Unit = {val placed: List[Point] = List(Point(0, 0), Point(1, 1))println(placed.mkString) // Point(0,0)Point(1,1)val moved = movement(Point(2, 2), placed)println(moved.mkString) //Point(2,2)Point(3,3)}def movement(move: Point, placed: List[Point]): List[Point] = {// here you create new list and don't mutate the old oneplaced.map(p => p + move)}case class Point(x: Int, y: Int) {def +(p: Point) = Point(x + p.x, y + p.y)}
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