IPropertyDatabaseView

描述

一个 PropertyDatabase 视图的接口。

一个 PropertyDatabase 视图的概念类似于 Windows 的内存映射文件视图，尽管简单许多。每个 PropertyDatabase 视图都有自己的文件流，它可以独立于其他视图来访问 PropertyDatabase。一个 PropertyDatabase 的视图是同步的，因此允许并发访问。然而，为了让并发访问正常工作，每个线程必须自己具有一个视图的实例。

在 PropertyDatabase 类中可用的所有操作都在视图本身中可用。直接在 PropertyDatabase 实例上操作时，将创建一个内部视图以处理所有同步。由于我们处理的是文件，因此打开一个视图的成本不可忽略。因此，建议打开一个视图，并在丢弃它之前尽可能长时间使用它。

using System.Collections.Generic;
using NUnit.Framework;
using UnityEditor;
using UnityEditor.Search;
using UnityEngine;

static class Example_IPropertyDatabaseView
{
    // Where the property database will be written.
    const string propertyDatabaseFilePath = "Temp/test_ipropertydatabaseview_db";

    static PropertyDatabase propertyDatabase;

    static void InitializePropertyDatabase()
    {
        // Setup the property database. We configure it with automatic flushing so the file store
        // will be updated automatically after an update.
        propertyDatabase = new PropertyDatabase(propertyDatabaseFilePath, true);
    }

    static void ClearPropertyDatabase()
    {
        propertyDatabase.Clear();
        propertyDatabase.Dispose();
    }

    static PropertyDatabaseRecordKey GetPropertyKey(int id, IPropertyDatabaseView view)
    {
        return view.CreateRecordKey((ulong)id / 100, view.CreatePropertyHash((id % 100).ToString()));
    }

    static object LoadPropertyValue(int id, IPropertyDatabaseView view)
    {
        var recordKey = GetPropertyKey(id, view);
        if (view.TryLoad(recordKey, out object value))
            return value;

        // Fetch the value with the time consuming operation and store it for future
        // accesses.
        value = id.ToString();
        view.Store(recordKey, value);
        return value;
    }

    [MenuItem("Examples/IPropertyDatabaseView/Interface")]
    public static void RunExample()
    {
        InitializePropertyDatabase();
        if (!propertyDatabase.valid)
        {
            Debug.LogFormat(LogType.Error, LogOption.NoStacktrace, null, $"PropertyDatabase \"{propertyDatabase.filePath}\" failed to open properly.");
            return;
        }

        // Doing a change on the property database internally opens a view on the actual data,
        // which is non negligible. Therefore, it is advised to open a view once and use it as much as you
        // can.
        // Note: when doing concurrent accesses to the property database, each thread must have its own
        // view instance.
        var allValues = new Dictionary<int, object>();
        using (var view = propertyDatabase.GetView())
        {
            for (var i = 0; i < 1000; ++i)
            {
                var value = LoadPropertyValue(i, view);
                allValues.Add(i, value);
            }
        }

        // Validate everything is in the database
        using (var view = propertyDatabase.GetView())
        {
            for (var i = 0; i < 1000; ++i)
            {
                var key = GetPropertyKey(i, view);
                if (!view.TryLoad(key, out object value))
                    Assert.Fail("Record should be in the database.");
                Assert.AreEqual(i.ToString(), value);
            }
        }

        ClearPropertyDatabase();
    }
}

其他资源：PropertyDatabase.GetView

公共方法