【发布时间】：2021-12-18 12:34:29
【问题描述】：
我刚开始使用 php oop 并遇到了错误。我似乎无法自己找到解决方案。 错误是：
致命错误：未捕获的错误：调用 C:\xampp\htdocs\dicegame\Game.php:26 中的成员函数 getFaceValue() 为 null 堆栈跟踪：#0 C:\xampp\htdocs\dicegame\index。 php(34): Game->play('3') #1 {main} 在第 26 行的 C:\xampp\htdocs\dicegame\Game.php 中抛出。
如果您知道答案或有任何提示，请告诉我！
index.php
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="utf-8">
<title>Dice Game </title>
<link rel="stylesheet" type="text/css" href="css/style.css">
</head>
<body>
<div id="container">
<header>
<?php
?>
</header>
<form action="index.php" method="POST">
<input type="number" name="quantity" value="3" id="quantity" min="3" max="8" placeholder="Number of dice"></br>
<input type="submit" name="throw" id="throwBtn" value="Roll">
</form>
<?php
include('NumberToThrow.php');
include('Dice.php');
include('Game.php');
$quantity = $_POST["quantity"] ?? "";
// start the game
if(isset($_POST['throw'])) {
echo "<h3>Throw the dices, baby ................. <br/></h3>";
$myGame = new Game();
$myGame->play($quantity);
}
?>
</div>
<footer ></footer>
</body>
</html>
game.php
<?php
class Game {
// class variables
private $diceValue;
private $throwNumber;
private $count;
private $dicesArray;
public function play($quantity) {
$this->createThrowNumber();
$this->count = 0;
$this->dicesArray = new SplFixedArray(8); // create array with length initially equals to 8
for ($index = 0; $index < $quantity; $index++)
{
$dice = new Dice(); // instantiate dice object
$dice->throwDice(); // make the throw
$this->dicesArray[$index] = $dice;
}
foreach($this->dicesArray as $dice) // The code in this foreach could also be implemented in
// the for-loop above, but for example these are seperated
{
$this->diceValue = $dice->getFaceValue(); // get the result of the throw & assign it to $diceValue
echo("</br>");
echo "The value of the dice: " . $this->diceValue . " ";
$this->showDiceImage($this->diceValue); // show value of throw as an image
echo("</br>");
if ($this->diceValue == $this->throwNumber) $this->count++;
}
// display statistics
if($this->count > 0) {
echo "</br>Number thrown: " . $this->count . " times.</br>";
}
else {
echo "</br>Number is not thrown.</br>";
}
}
public function createThrowNumber() {
$numberObject = new NumberToThrow(); // instantiate object - instance of the NumberToThrow class
$this->throwNumber = $numberObject->makeAThrow(); // make a number to throw
echo "<p>Your number to throw: <b>" . $this->throwNumber . "</b></p>";
$this->showDiceImage($this->throwNumber); // show the number to throw as dice image
echo "</br>";
}
public function showDiceImage($dots) {
switch($dots) {
case 1:
echo "<img class='dotsImg' src='images/d1.png'>";
break;
case 2:
echo "<img class='dotsImg' src='images/d2.png'>";
break;
case 3:
echo "<img class='dotsImg' src='images/d3.png'>";
break;
case 4:
echo "<img class='dotsImg' src='images/d4.png'>";
break;
case 5:
echo "<img class='dotsImg' src='images/d5.png'>";
break;
case 6:
echo "<img class='dotsImg' src='images/d6.png'>";
break;
default:
break;
}
}
}
?>
Dice.php
<?php
class Dice {
const NUMBER_OF_SIDES = 6;
private $faceValue;
public function throwDice() {
$this->faceValue = rand(1, self::NUMBER_OF_SIDES); // 1 & NUMBER_OF_SIDES are inclusive values
}
public function getFaceValue() {
return $this->faceValue;
}
}
?>
【问题讨论】：
-
你为什么要使用
SplFixedArray，如果很明显你的数组没有固定数量的元素？如果你这样做了，请使用$quantity来初始化SplFixedArray($quantity)，这样你的数组就只有你期望的大小，而不是你可以迭代的空。