Inventor API代码性能优化 - 2

上篇我们谈到一些场景。本篇我们先来看看VBA编程可以优化的方面。大家熟悉的，VBA里有个缺省的对象ThisApplication，它是Inventor API的顶层入口。用起来比较方便，但其实会有所消耗，以下面的代码为例，它访问Locale属性10万次，花费了74.8 秒（进程外的话）。

Public Sub CallCost() 
    Dim timer As New clsTimer 
    timer.Start 

    Dim i As Long 
    For i = 1 To 100000 
        Dim code As Long 
        code = ThisApplication.Locale 
    Next 

    Debug.Print "Total time: " & Format(timer.GetTime, "0.00000") 
End Sub

而稍作改动，将只需要18.8秒。可以注意到其先是获取到app，然后调用10万次。原理很简单，前面的ThisApplication相当于每次都取用ThisApplication，存在读取调用，而后者只是调用一次，接下来都是引用。

Public Sub CallCost() 
    Dim timer As New clsTimer 
    timer.Start 

    <span style="background-color: rgb(255, 255, 102);">Dim app As Inventor.Application</span> 
    <span style="background-color: rgb(255, 255, 51);">Set app = ThisApplication</span> 

    Dim i As Long 
    For i = 1 To 100000 
        Dim code As Long 
        code = <span style="background-color: rgb(255, 255, 51);">app.Locale</span> 
    Next 

    Debug.Print "Total time: " & Format(timer.GetTime, "0.00000") 
End Sub

引用而非内联函数调用

再来一个优化，和前面类似，就是当您需要频繁调用某个对象时，尽量引用。这里有段代码遍历装配体的所有部件，获取其名字和对应的文件名。一个有500个部件的装配，循环调用10次，大约花了22.5秒。

Public Sub GetOccurrences1() 
    Dim asmDoc As AssemblyDocument 
    Set asmDoc = ThisApplication.ActiveDocument 

    Dim i As Integer 
    For i = 1 To asmDoc.ComponentDefinition.Occurrences.Count 
        Dim Name As String 
        Name = asmDoc.ComponentDefinition.Occurrences.Item(i).Name 

        Dim filename As String 
        filename = asmDoc.ComponentDefinition.Occurrences.Item(i). _ 
                   ReferencedDocumentDescriptor. _ 
                   ReferencedFileDescriptor.FullFileName 
    Next 
End Sub

让我们稍作改动如下, 时间减少到9.7秒。

Public Sub GetOccurrences2() 
    Dim asmDoc As AssemblyDocument 
    Set asmDoc = ThisApplication.ActiveDocument 

    <span style="background-color: rgb(255, 255, 51);">Dim occs As ComponentOccurrences </span>
    <span style="background-color: rgb(255, 255, 51);">Set occs = asmDoc.ComponentDefinition.Occurrences</span> 

    Dim i As Integer 
    For i = 1 To occs.Count 
        Dim Occ As ComponentOccurrence 
        Set Occ = occs.Item(i) 

        Dim Name As String 
        Name = Occ.Name 

        Dim filename As String 
        <span style="background-color: rgb(255, 255, 51);">filename = Occ.ReferencedDocumentDescriptor. _ 
                        ReferencedFileDescriptor.FullFileName</span> 
    Next 
End Sub

使用For Each而不要Count 和Item

还是以便利装配中的部件为例，以下代码将花费9.4秒。虽然比前面并未有明显改变，但不同的集合会有不同的时间优化。而且，也比count item好阅读些，对吧。
背后的故事是因为使用For Each的时候，Inventor提前知道您讲遍历一个集合，就会先从内部优化。而count item的模式，Inventor不知您是遍历一次呢，还是多次呢，还是整个集合，所以提前不会做什么优化工作。

Public Sub GetOccurrences3() 
    Dim asmDoc As AssemblyDocument 
    Set asmDoc = ThisApplication.ActiveDocument 

    Dim occs As ComponentOccurrences 
    Set occs = asmDoc.ComponentDefinition.Occurrences 

    Dim Occ As ComponentOccurrence 
   <span style="background-color: rgb(255, 255, 51);"> For Each Occ In occs </span>
        Dim Name As String 
        Name = Occ.Name 

        Dim filename As String 
        filename = Occ.ReferencedDocumentDescriptor. _ 
                   ReferencedFileDescriptor.FullFileName 
    Next 
End Sub

通过名字过去某条目Item

和集合关联的另外一种优化就是，假设要获取集合内某个对象条目，尽量用名字获取，而不要遍历一个个查找。例如，这段代码想获得某个TranslatorAddIn.

Dim dxfAddIn As TranslatorAddIn 
For i = 1 To addIns.Count 
    If addIns(i).AddInType = kTranslationApplicationAddIn Then 
        Dim desc As String 
        desc = addIns(i).Description   
        If desc = "Autodesk Internal DXF Translator" Then 
            Set dxfAddIn = addIns.Item(i) 
            Exit For 
        End If 
    End If 
Next

而下面这段代码，不仅效率提高，而且也美观些。

Dim dxfAddIn As TranslatorAddIn 
Set dxfAddIn = addIns. _ 
                 ItemById("{C24E3AC4-122E-11D5-8E91-0010B541CD80}")