Godot接口

通常，一个人需要依赖于其他对象的脚本来获取特性。这个过程有两个部分：

1. 获取对可能具有特征的对象的引用。

2. 从对象访问数据或逻辑。

本教程的其余部分概述了执行所有这些操作的各种方法。

获取对象引用

为了所有 Object s，引用它们的最基本方法是从另一个获取的实例获取对现有对象的引用。

GDScript

C#

var obj = node.object # Property access.
var obj = node.get_object() # Method access.

Object obj = node.Object; // Property access.
Object obj = node.GetObject(); // Method access.

同样的原则也适用于 Reference 物体。用户经常访问 Node 和 Resource 这样，就可以采取其他措施。

可以通过加载访问来获取资源，而不是属性或方法访问。

GDScript

C#

var preres = preload(path) # Load resource during scene load
var res = load(path) # Load resource when program reaches statement

# Note that users load scenes and scripts, by convention, with PascalCase
# names (like typenames), often into constants.
const MyScene : = preload("my_scene.tscn") as PackedScene # Static load
const MyScript : = preload("my_script.gd") as Script

# This type's value varies, i.e. it is a variable, so it uses snake_case.
export(Script) var script_type: Script

# If need an "export const var" (which doesn't exist), use a conditional
# setter for a tool script that checks if it's executing in the editor.
tool # Must place at top of file.

# Must configure from the editor, defaults to null.
export(Script) var const_script setget set_const_script
func set_const_script(value):
    if Engine.is_editor_hint():
        const_script = value

# Warn users if the value hasn't been set.
func _get_configuration_warning():
    if not const_script:
        return "Must initialize property 'const_script'."
    return ""

// Tool script added for the sake of the "const [Export]" example.
[Tool]
public MyType : extends Object
{
    // Property initializations load during Script instancing, i.e. .new().
    // No "preload" loads during scene load exists in C#.

    // Initialize with a value. Editable at runtime.
    public Script MyScript = GD.Load<Script>("MyScript.cs");

    // Initialize with same value. Value cannot be changed.
    public readonly Script MyConstScript = GD.Load<Script>("MyScript.cs");

    // Like 'readonly' due to inaccessible setter.
    // But, value can be set during constructor, i.e. MyType().
    public Script Library { get; } = GD.Load<Script>("res://addons/plugin/library.gd");

    // If need a "const [Export]" (which doesn't exist), use a
    // conditional setter for a tool script that checks if it's executing
    // in the editor.
    private PackedScene _enemyScn;

    [Export]
    public PackedScene EnemyScn
    {
        get { return _enemyScn; }
        set
        {
            if (Engine.IsEditorHint())
            {
                _enemyScn = value;
            }
        }
    };

    // Warn users if the value hasn't been set.
    public String _GetConfigurationWarning()
    {
        if (EnemyScn == null)
            return "Must initialize property 'EnemyScn'.";
        return "";
    }
}

注意以下事项：

1. 语言可以通过多种方式加载此类资源。

2. 在设计对象访问数据的方式时，不要忘记可以将资源作为引用传递。

3. 请记住，加载资源会获取由引擎维护的缓存资源实例。要获得新对象，必须 duplicate 现有的引用或用 new() .

节点也有另一个访问点：scenetree。

GDScript

C#

extends Node

# Slow.
func dynamic_lookup_with_dynamic_nodepath():
    print(get_node("Child"))

# Faster. GDScript only.
func dynamic_lookup_with_cached_nodepath():
    print($Child)

# Fastest. Doesn't break if node moves later.
# Note that `onready` keyword is GDScript only.
# Other languages must do...
#     var child
#     func _ready():
#         child = get_node("Child")
onready var child = $Child
func lookup_and_cache_for_future_access():
    print(child)

# Delegate reference assignment to an external source
# Con: need to perform a validation check
# Pro: node makes no requirements of its external structure.
#      'prop' can come from anywhere.
var prop
func call_me_after_prop_is_initialized_by_parent():
    # Validate prop in one of three ways.

    # Fail with no notification.
    if not prop:
        return

    # Fail with an error message.
    if not prop:
        printerr("'prop' wasn't initialized")
        return

    # Fail and terminate.
    # Compiled scripts in final binary do not include assert statements
    assert prop.

# Use an autoload.
# Dangerous for typical nodes, but useful for true singleton nodes
# that manage their own data and don't interfere with other objects.
func reference_a_global_autoloaded_variable():
    print(globals)
    print(globals.prop)
    print(globals.my_getter())

public class MyNode
{
    // Slow, dynamic lookup with dynamic NodePath.
    public void Method1()
    {
        GD.Print(GetNode(NodePath("Child")));
    }

    // Fastest. Lookup node and cache for future access.
    // Doesn't break if node moves later.
    public Node Child;
    public void _Ready()
    {
        Child = GetNode(NodePath("Child"));
    }
    public void Method2()
    {
        GD.Print(Child);
    }

    // Delegate reference assignment to an external source
    // Con: need to perform a validation check
    // Pro: node makes no requirements of its external structure.
    //      'prop' can come from anywhere.
    public object Prop;
    public void CallMeAfterPropIsInitializedByParent()
    {
        // Validate prop in one of three ways.

        // Fail with no notification.
        if (prop == null)
        {
            return;
        }

        // Fail with an error message.
        if (prop == null)
        {
            GD.PrintErr("'Prop' wasn't initialized");
            return;
        }

        // Fail and terminate.
        Debug.Assert(Prop, "'Prop' wasn't initialized");
    }

    // Use an autoload.
    // Dangerous for typical nodes, but useful for true singleton nodes
    // that manage their own data and don't interfere with other objects.
    public void ReferenceAGlobalAutoloadedVariable()
    {
        Node globals = GetNode(NodePath("/root/Globals"));
        GD.Print(globals);
        GD.Print(globals.prop);
        GD.Print(globals.my_getter());
    }
};

从对象访问数据或逻辑

Godot的脚本API是duck类型的。这意味着，如果脚本执行操作，Godot不会通过以下方式验证它是否支持该操作： type . 而是检查对象 器具 个人方法。

例如， CanvasItem 类有 visible 属性。向脚本API公开的所有属性实际上都是绑定到名称的setter和getter对。如果有人试图进入 CanvasItem.visible ，那么Godot将按顺序进行以下检查：

• 如果对象附加了脚本，它将尝试通过脚本设置属性。这样，脚本就有机会通过重写属性的setter方法来重写在基对象上定义的属性。

• 如果脚本没有该属性，它将在ClassDB中对CanvasItem类及其所有继承类型执行“可见”属性的哈希映射查找。如果找到，它将调用绑定的setter或getter。有关HashMaps的详细信息，请参阅 data preferences。

• 如果找不到，它将进行显式检查，以查看用户是否希望访问“script”或“meta”属性。

• 如果没有，它会检查 _set/_get canvasItem及其继承类型中的实现（取决于访问类型）。这些方法可以执行逻辑，让人觉得对象有一个属性。这也适用于 _get_property_list 方法。

  • 请注意，这种情况甚至发生在非法定符号名称中，例如 TileSet 'S“1/瓷砖名称”属性。这是指ID为1的图块的名称，即 TileSet.tile_get_name(1) .

因此，这个duck类型的系统可以在脚本、对象的类或对象继承的任何类中定位属性，但只能定位扩展对象的对象。

godot提供了各种选项，用于对这些访问执行运行时检查：

• Duck式财产访问。这些将进行属性检查（如上所述）。如果对象不支持该操作，则将停止执行。

  GDScript

  C#

  # All Objects have duck-typed get, set, and call wrapper methods.
  get_parent().set("visible", false)
  
  # Using a symbol accessor, rather than a string in the method call,
  # will implicitly call the `set` method which, in turn, calls the
  # setter method bound to the property through the property lookup
  # sequence.
  get_parent().visible = false
  
  # Note that if one defines a _set and _get that describe a property's
  # existence, but the property isn't recognized in any _get_property_list
  # method, then the set() and get() methods will work, but the symbol
  # access will claim it can't find the property.
  

  // All Objects have duck-typed Get, Set, and Call wrapper methods.
  GetParent().Set("visible", false);
  
  // C# is a static language, so it has no dynamic symbol access, e.g.
  // `GetParent().Visible = false` won't work.
  

• 方法检查。如果是 CanvasItem.visible 可以访问这些方法， set_visible 和 is_visible 像其他方法一样。

  GDScript

  C#

  var child = get_child(0)
  
  # Dynamic lookup.
  child.call("set_visible", false)
  
  # Symbol-based dynamic lookup.
  # GDScript aliases this into a 'call' method behind the scenes.
  child.set_visible(false)
  
  # Dynamic lookup, checks for method existence first.
  if child.has("set_visible"):
      child.set_visible(false)
  
  # Cast check, followed by dynamic lookup
  # Useful when you make multiple "safe" calls knowing that the class
  # implements them all. No need for repeated checks.
  # Tricky if one executes a cast check for a user-defined type as it
  # forces more dependencies.
  if child is CanvasItem:
      child.set_visible(false)
      child.show_on_top = true
  
  # If one does not wish to fail these checks without notifying users, one
  # can use an assert instead. These will trigger runtime errors
  # immediately if not true.
  assert child.has("set_visible")
  assert child.is_in_group("offer")
  assert child is CanvasItem
  
  # Can also use object labels to imply an interface, i.e. assume it implements certain methods.
  # There are two types, both of which only exist for Nodes: Names and Groups
  
  # Assuming...
  # A "Quest" object exists and 1) that it can "complete" or "fail" and
  # that it will have text available before and after each state...
  
  # 1. Use a name.
  var quest = $Quest
  print(quest.text)
  quest.complete() # or quest.fail()
  print(quest.text) # implied new text content
  
  # 2. Use a group.
  for a_child in get_children():
      if a_child.is_in_group("quest"):
          print(quest.text)
          quest.complete() # or quest.fail()
          print(quest.text) # implied new text content
  
  # Note that these interfaces are project-specific conventions the team
  # defines (which means documentation! But maybe worth it?).
  # Any script that conforms to the documented "interface" of the name/group can fill in for it.
  

  Node child = GetChild(0);
  
  // Dynamic lookup.
  child.Call("SetVisible", false);
  
  // Dynamic lookup, checks for method existence first.
  if (child.HasMethod("SetVisible"))
  {
      child.Call("SetVisible", false);
  }
  
  // Use a group as if it were an "interface", i.e. assume it implements certain methods
  // requires good documentation for the project to keep it reliable (unless you make
  // editor tools to enforce it at editor time.
  // Note, this is generally not as good as using an actual interface in C#,
  // but you can't set C# interfaces from the editor since they are
  // language-level features.
  if (child.IsInGroup("Offer"))
  {
      child.Call("Accept");
      child.Call("Reject");
  }
  
  // Cast check, followed by static lookup.
  CanvasItem ci = GetParent() as CanvasItem;
  if (ci != null)
  {
      ci.SetVisible(false);
  
      // useful when you need to make multiple safe calls to the class
      ci.ShowOnTop = true;
  }
  
  // If one does not wish to fail these checks without notifying users, one
  // can use an assert instead. These will trigger runtime errors
  // immediately if not true.
  Debug.Assert(child.HasMethod("set_visible"));
  Debug.Assert(child.IsInGroup("offer"));
  Debug.Assert(CanvasItem.InstanceHas(child));
  
  // Can also use object labels to imply an interface, i.e. assume it implements certain methods.
  // There are two types, both of which only exist for Nodes: Names and Groups
  
  // Assuming...
  // A "Quest" object exists and 1) that it can "Complete" or "Fail" and
  // that it will have Text available before and after each state...
  
  // 1. Use a name.
  Node quest = GetNode("Quest");
  GD.Print(quest.Get("Text"));
  quest.Call("Complete"); // or "Fail".
  GD.Print(quest.Get("Text")); // Implied new text content.
  
  // 2. Use a group.
  foreach (Node AChild in GetChildren())
  {
      if (AChild.IsInGroup("quest"))
      {
        GD.Print(quest.Get("Text"));
        quest.Call("Complete"); // or "Fail".
        GD.Print(quest.Get("Text")); // Implied new text content.
      }
  }
  
  // Note that these interfaces are project-specific conventions the team
  // defines (which means documentation! But maybe worth it?)..
  // Any script that conforms to the documented "interface" of the
  // name/group can fill in for it. Also note that in C#, these methods
  // will be slower than static accesses with traditional interfaces.
  

• 将访问权限外包给 FuncRef . 在需要从依赖关系中获得最大程度的自由的情况下，这些可能很有用。在这种情况下，需要依赖外部上下文来设置方法。

GDScript

C#

# child.gd
extends Node
var fn = null

func my_method():
    if fn:
        fn.call_func()

# parent.gd
extends Node

onready var child = $Child

func _ready():
    child.fn = funcref(self, "print_me")
    child.my_method()

func print_me():
    print(name)

// Child.cs
public class Child extends Node
{
    public FuncRef FN = null;

    public void MyMethod()
    {
        Debug.Assert(FN != null);
        FN.CallFunc();
    }
}

// Parent.cs
public class Parent extends Node
{
    public Node Child;

    public void _Ready()
    {
        Child = GetNode("Child");
        Child.Set("FN", GD.FuncRef(this, "PrintMe"));
        Child.MyMethod();
    }

    public void PrintMe() {
    {
        GD.Print(GetClass());
    }
}

这些策略有助于Godot的灵活设计。在它们之间，用户有各种各样的工具来满足他们的特定需求。