PropertyVisitor 创建属性访问器此示例演示如何使用 PropertyVisitor 基类创建属性访问器。关于使用 IPropertyBagVisitor 和 IPropertyVisitor 接口的等效示例，请参阅 使用低级API创建属性访问器。
此示例包括创建一个属性访问器的逐步说明，该访问器将打印对象当前状态到控制台。
假设你有一个以下类型
public class Data
{
public string Name = "Henry";
public Vector2 Vec2 = Vector2.one;
public List<Color> Colors = new List<Color> { Color.green, Color.red };
public Dictionary<int, string> Dict = new Dictionary<int, string> {{5, "zero"}};
}
创建一个类似这样的实用方法 DebugUtilities
public static class DebugUtilities
{
public static void PrintObjectDump<T>(T value)
{
// Magic goes here.
}
}
如下调用 PrintObjectDump 方法使用 Data 对象
DebugUtilities.PrintObjectDump(new Data());
将在控制台打印以下内容
- Name {string} = Henry
- Vec2 {Vector2} = (1.00, 1.00)
- Colors {List<Color>}
- [0] = {Color} RGBA(0.000, 1.000, 0.000, 1.000)
- [1] = {Color} RGBA(1.000, 0.000, 0.000, 1.000)
- Dict {Dictionary<int, string>}
- [5] {KeyValuePair<int, string>}
- Key {int} = 5
- Value {string} = five
首先，创建一个 DumpObjectVisitor 类。在类中，使用一个 StringBuilder 构建表示对象当前状态的字符串。
创建一个继承自 PropertyVisitor 的 DumpObjectVisitor 类。
向类中添加一个 StringBuilder 字段。
添加一个 Reset 方法，它清除 StringBuilder 并重置缩进级别。
添加一个 GetDump 方法，它返回对象当前状态字符串表示。
你的最终类看起来像这样
// `PropertyVisitor` is an abstract class that you must subclass from it.
public class DumpObjectVisitor: PropertyVisitor
{
private const int k_InitialIndent = 0;
private readonly StringBuilder m_Builder = new StringBuilder();
private int m_IndentLevel = k_InitialIndent;
private string Indent => new (' ', m_IndentLevel * 2);
public void Reset()
{
m_Builder.Clear();
m_IndentLevel = k_InitialIndent;
}
public string GetDump()
{
return m_Builder.ToString();
}
}
在 DumpObjectVisitor 类中，重写 VisitProperty 方法来遍历对象的每个属性并记录属性名称。默认情况下，`PropertyVisitor` 不需要实现任何成员并且简单地遍历每个属性不执行任何操作。
在 DumpObjectVisitor 类中，添加以下重写的 VisitProperty 方法
protected override void VisitProperty<TContainer, TValue>(Property<TContainer, TValue> property, ref TContainer container, ref TValue value)
{
m_Builder.AppendLine($"- {property.Name}");
}
现在你已经有了最小的访问器，可以实现实用方法。更新 DebugUtilities 类中的 PrintObjectDump 方法以创建一个新的 DumpObjectVisitor 实例并使用它来遍历给定对象的属性
public static class DebugUtilities
{
private static readonly DumpObjectVisitor s_Visitor = new ();
public static void PrintObjectDump<T>(T value)
{
s_Visitor.Reset();
// This is the main entry point to run a visitor.
PropertyContainer.Accept(s_Visitor, ref value);
Debug.Log(s_Visitor.GetDump());
}
}
这将得到以下输出
- Name
- Vec2
- Colors
- Dict
上一节中的输出表明，当你重写 VisitProperty 方法时，它不会自动遍历对象的子属性。要获取子属性，请使用 PropertyContainer.Accept 方法递归地应用访问器到每个值。
在 DebugUtilities 类中，更新 VisitProperty 方法以递归地应用访问器到嵌套值
protected override void VisitProperty<TContainer, TValue>(Property<TContainer, TValue> property, ref TContainer container, ref TValue value)
{
m_Builder.AppendLine($"{Indent}- {property.Name}");
++m_IdentLevel;
// Apply this visitor recursively on the value to nest in.
if (null != value)
PropertyContainer.Accept(this, ref value);
--m_IdentLevel;
}
这将得到以下输出
- Name
- Vec2
- x
- y
- Colors
- 0
- r
- g
- b
- a
- 1
- r
- g
- b
- a
- Dict
- 5
- Key
- Value
接下来，让我们获取集合项的属性名以及每个属性的类型和值。
某些属性有特殊名称，尤其是在处理集合项时。这里有属性名的约定
为了更明确地区分，将属性名括在方括号中。
在 DumpObjectVisitor 类中，添加以下方法
private static string GetPropertyName(IProperty property)
{
return property switch
{
// You can also treat `IListElementProperty`, `IDictionaryElementProperty`, and `ISetElementProperty` separately.
ICollectionElementProperty => $"[{property.Name}]",
_ => property.Name
};
}
更新 VisitProperty 方法以使用 TypeUtility.GetTypeDisplayName 获取给定类型的显示名称。
protected override void VisitProperty<TContainer, TValue>(Property<TContainer, TValue> property, ref TContainer container, ref TValue value)
{
var propertyName = GetPropertyName(property);
// Get the concrete type of the property or its declared type if value is null.
var typeName = TypeUtility.GetTypeDisplayName(value?.GetType() ?? property.DeclaredValueType());
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{typeName}}} {value}");
++m_IndentLevel;
if (null != value)
PropertyContainer.Accept(this, ref value);
--m_IndentLevel;
}
这将得到以下输出
- Name = {string} Henry
- Vec2 = {Vector2} (1.00, 1.00)
- x = {float} 1
- y = {float} 1
- Colors = {List<Color>} System.Collections.Generic.List`1[UnityEngine.Color]
- [1] = {Color} RGBA(0.000, 1.000, 0.000, 1.000)
- r = {float} 0
- g = {float} 1
- b = {float} 0
- a = {float} 1
- [1] = {Color} RGBA(1.000, 0.000, 0.000, 1.000)
- r = {float} 1
- g = {float} 0
- b = {float} 0
- a = {float} 1
- Dict = {Dictionary<int, string>} System.Collections.Generic.Dictionary`2[System.Int32,System.String]
- [5] = {KeyValuePair<int, string>} [5, five]
- Key = {int} 5
- Value = {string} five
因为 List<T> 没有覆盖 ToString() 方法，所以列表值显示为 System.Collections.Generic.List1[UnityEngine.Color]。为了减少显示的信息量，更新 VisitProperty 以使用 TypeTraits.IsContainer 工具方法来只为不包含子属性的类型显示值，例如基本类型、枚举和字符串。
在 DumpObjectVisitor 类内部，更新 VisitProperty 方法以使用 TypeTraits.IsContainer 来确定值是否为容器类型。如果是容器类型，则显示类型名称而不显示值。否则，显示类型名称和值。
protected override void VisitProperty<TContainer, TValue>(Property<TContainer, TValue> property, ref TContainer container, ref TValue value)
{
var propertyName = GetPropertyName(property);
var type = value?.GetType() ?? property.DeclaredValueType();
var typeName = TypeUtility.GetTypeDisplayName(type);
// Only display the values for primitives, enums and strings.
if (TypeTraits.IsContainer(type))
m_Builder.AppendLine($"{Indent}- {propertyName} {{{typeName}}}");
else
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{typeName}}} {value}");
++m_IndentLevel;
if (null != value)
PropertyContainer.Accept(this, ref value);
--m_IndentLevel;
}
这将得到以下输出
- Name = {string} Henry
- Vec2 {Vector2}
- x = {float} 1
- y = {float} 1
- Colors {List<Color>}
- [0] {Color}
- r = {float} 0
- g = {float} 1
- b = {float} 0
- a = {float} 1
- [1] {Color}
- r = {float} 1
- g = {float} 0
- b = {float} 0
- a = {float} 1
- Dict {Dictionary<int, string>}
- [5] {KeyValuePair<int, string>}
- Key = {int} 5
- Value = {string} five
提示:
为了减少显示的信息量，您还可以使用以下方法覆盖集合类型的 Visit 特化
protected override void VisitCollection<TContainer, TCollection, TElement>(Property<TContainer, TCollection> property, ref TContainer container, ref TCollection value) {}
protected override void VisitList<TContainer, TList, TElement>(Property<TContainer, TList> property, ref TContainer container, ref TList value) {}
protected override void VisitDictionary<TContainer, TDictionary, TKey, TValue>(Property<TContainer, TDictionary> property, ref TContainer container, ref TDictionary value) {}
protected override void VisitSet<TContainer, TSet, TValue>(Property<TContainer, TSet> property, ref TContainer container, ref TSet value) {}
这些与 VisitProperty 方法类似，但它们公开了各自集合类型的泛型参数。
最后，添加特定类型的覆盖来更紧凑地显示 Vector2 和 Color 类型。
使用 PropertyVisitor 与 IVisitPropertyAdapter。每当为特定类型注册了适配器时，如果遇到目标类型，则调用适配器而不是 VisitProperty 方法
在 DumpObjectVisitor 类内部，为 Vector2 和 Color 添加 IVisitPropertyAdapter
public class DumpObjectVisitor
: PropertyVisitor
, IVisitPropertyAdapter<Vector2>
, IVisitPropertyAdapter<Color>
{
public DumpObjectVisitor()
{
AddAdapter(this);
}
void IVisitPropertyAdapter<Vector2>.Visit<TContainer>(in VisitContext<TContainer, Vector2> context, ref TContainer container, ref Vector2 value)
{
var propertyName = GetPropertyName(context.Property);
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{nameof(Vector2)}}} {value}");
}
void IVisitPropertyAdapter<Color>.Visit<TContainer>(in VisitContext<TContainer, Color> context, ref TContainer container, ref Color value)
{
var propertyName = GetPropertyName(context.Property);
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{nameof(Color)}}} {value}");
}
}
完成的 DumpObjectVisitor 类看起来如下所示
public class DumpObjectVisitor
: PropertyVisitor
, IVisitPropertyAdapter<Vector2>
, IVisitPropertyAdapter<Color>
{
private const int k_InitialIndent = 0;
// StringBuilder to store the dumped object's properties and values.
private readonly StringBuilder m_Builder = new StringBuilder();
private int m_IndentLevel = k_InitialIndent;
// Helper property to get the current indentation.
private string Indent => new (' ', m_IndentLevel * 2);
public DumpObjectVisitor()
{
// Constructor, it initializes the DumpObjectVisitor and adds itself as an adapter
// to handle properties of type Vector2 and Color.
AddAdapter(this);
}
// Reset the visitor, clearing the StringBuilder and setting indentation to initial level.
public void Reset()
{
m_Builder.Clear();
m_IndentLevel = k_InitialIndent;
}
// Get the string representation of the dumped object.
public string GetDump()
{
return m_Builder.ToString();
}
// Helper method to get the property name, handling collections and other property types.
private static string GetPropertyName(IProperty property)
{
return property switch
{
// If it's a collection element property, display it with brackets
ICollectionElementProperty => $"[{property.Name}]",
// For other property types, display the name as it is
_ => property.Name
};
}
// This method is called when visiting each property of an object.
// It determines the type of the value and formats it accordingly for display.
protected override void VisitProperty<TContainer, TValue>(Property<TContainer, TValue> property, ref TContainer container, ref TValue value)
{
var propertyName = GetPropertyName(property);
// Get the type of the value or property.
var type = value?.GetType() ?? property.DeclaredValueType();
var typeName = TypeUtility.GetTypeDisplayName(type);
// Only display the values for primitives, enums, and strings, and treat other types as containers.
if (TypeTraits.IsContainer(type))
m_Builder.AppendLine($"{Indent}- {propertyName} {{{typeName}}}");
else
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{typeName}}} {value}");
// Increase indentation level before visiting child properties (if any).
++m_IndentLevel;
if (null != value)
PropertyContainer.Accept(this, ref value);
// Decrease indentation level after visiting child properties.
--m_IndentLevel;
}
// This method is a specialized override for Vector2 properties.
// It displays the property name and its value as a Vector2.
void IVisitPropertyAdapter<Vector2>.Visit<TContainer>(in VisitContext<TContainer, Vector2> context, ref TContainer container, ref Vector2 value)
{
var propertyName = GetPropertyName(context.Property);
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{nameof(Vector2)}}} {value}");
}
// This method is a specialized override for Color properties.
// It displays the property name and its value as a Color.
void IVisitPropertyAdapter<Color>.Visit<TContainer>(in VisitContext<TContainer, Color> context, ref TContainer container, ref Color value)
{
var propertyName = GetPropertyName(context.Property);
m_Builder.AppendLine($"{Indent}- {propertyName} = {{{nameof(Color)}}} {value}");
}
}
当在数据上运行访问者时，默认情况下，它直接从给定的对象开始遍历。对于任何属性访问者，要开始遍历对象的子属性，请将 PropertyPath 传递给 PropertyContainer.Accept 方法。
更新 DebugUtilities 方法以接受可选的 PropertyPath
public static class DebugUtilities
{
private static readonly DumpObjectVisitor s_Visitor = new();
public static void PrintObjectDump<T>(T value, PropertyPath path = default)
{
s_Visitor.Reset();
if (path.IsEmpty)
PropertyContainer.Accept(s_Visitor, ref value);
else
PropertyContainer.Accept(s_Visitor, ref value, path);
Debug.Log(s_Visitor.GetDump());
}
}
使用 Data 对象调用 PrintObjectDump 方法。这将获得希望得到的输出。