教程二 · 第 2 章：运算符、流程控制、方法#

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int a = 10, b = 3;
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GD.Print(a + b);   // 13
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GD.Print(a / b);   // 3！整数除整数还是整数（截断）
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GD.Print(a % b);   // 1，取余：判断整除、循环索引超有用
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GD.Print(10f / 3f);// 3.333...，想要小数结果至少一边是 float/double
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a++;       // 等同 a = a + 1
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a += 5;    // 等同 a = a + 5，-= *= /= 同理
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GD.Print(2 + 3 * 4); // 14，先乘除后加减，拿不准就加括号

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_attackCooldown -= dt;
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if (_enemiesKilled % 5 == 0) GD.Print("每杀 5 个触发一次");

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bool isLow = hp < 30;
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bool canAct = hp > 0 && isGrounded;  // && 与：两边都真
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bool hit = wasAttacked || steppedTrap; // || 或：任一为真
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bool notGrounded = !isGrounded;       // ! 非
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if (hp >= 0 && hp <= 100) { }        // 区间判断要写两遍，不能 0 <= hp <= 100

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if (_target != null && _target.IsInsideTree()) { } // 安全：先确认存在

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string stateName = isGrounded ? "地面" : "空中";
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// 等价于
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// string stateName;
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// if (isGrounded) stateName = "地面"; else stateName = "空中";

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Velocity = Velocity with { X = dir != 0 ? dir * speed : Velocity.X };

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SetCollisionLayerValue(2, true);                 // 打开第 2 层
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uint mask = CollisionMask;
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bool hitsLayer3 = (mask & (1u << 2)) != 0;       // 检查第 3 位

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Node collider = collisionInfo.GetCollider();
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if (collider is Paddle paddle)   // 类型检查 + 转换一步完成
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{
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    BounceFromPaddle(paddle);    // paddle 已当作 Paddle 类型可用
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}
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else if (collider is StaticBody2D)
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{
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    _direction.Y = -_direction.Y;
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}

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if (collider is Paddle)
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{
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    var paddle = (Paddle)collider; // 先判断再强转，啰嗦
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}

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if (collider is Enemy { Hp: <= 0 }) return; // 是敌人且血量已为 0

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float damageMult = element switch
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{
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    DamageType.Physical => 1.0f,
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    DamageType.Fire => 1.5f,
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    DamageType.Ice => 0.8f,
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    _ => 1.0f                          // _ 是"其他所有情况"
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};

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int bullets = 3;
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while (bullets > 0)
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{
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    FireOneShot();
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    bullets--;
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}

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for (int i = 0; i < 5; i++)
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{
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    GD.Print($"第 {i} 发"); // 0,1,2,3,4
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}

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foreach (Node child in GetChildren())
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{
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    child.QueueFree();
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}
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foreach (var node in GetTree().GetNodesInGroup("enemy"))
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{
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    if (node is Enemy enemy)
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        enemy.TakeDamage(10);
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}

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break;     // 立刻结束整个循环
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continue;  // 跳过本轮剩余语句，进入下一轮

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var collisions = MoveAndSlideCollide();
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for (int i = 0; i < collisions.Count; i++)
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{
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    var c = collisions[i];
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    // ...
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}

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void AddOne(int x) { x++; }
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AddOne(hp); // hp 本身不变

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void Kill(Player p) { p.Hp = 0; } // 外面那个 Player 真的被改

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if (PhysicsIntersectPoint(point, out var enemy))
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{
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    enemy.TakeDamage(10); // Godot 很多 TryGet 风格 API 都是 out 参数
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}

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public void Heal(int amount) { _hp += amount; }
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public void Heal(float percent) { _hp += (int)(MaxHp * percent); } // 同名不同参，合法

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private void SpawnEnemy(string type = "slime", int count = 1, float delay = 0f)
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SpawnEnemy();                     // slime, 1, 0
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SpawnEnemy("bat", 3);
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SpawnEnemy(count: 5, delay: 2f);  // 命名参数可跳过默认值，顺序随意

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public override void _PhysicsProcess(double delta)
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{
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    ApplyGravity(delta);
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    HandleInput();
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    UpdateStateMachine();
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    MoveAndSlide();
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}