[数学]理解对象模型图OMD.ppt

设置属性 Property Put：Most ArcObjects properties 属性获得一个值或一个对象的副本 不使用Set关键字 pLayer.Name=“Port Moresby” ‘No Set Keyword Property Put by Reference:Some ArcObjects properties 属性获得一个对象的引用即需要传入一地址 必须使用Set关键字 Set pLayer.FeatureClass=pMoresbyData ‘Must use Set IFeatureLayer Interface 帮助 七、查找接口 这些接口也是有效的。但是详细的 属性和方法必须在其它地方浏览。 (e.g., Object Browser). 该接口被本类使用. 所有的属性和放都列表在类图中. 继承接口是有效的 类继承要查找父类的接口 接口继承的属性和方法 示例：接口 八、虫孔 FeatureLayer on Map Layer OMD Element on ArcMap OMD 虫孔 Example: MxDocument Map layer Get the FocusMap (active data frame) from MxDocument MxDocument may have several Maps ( * ) Get a layer from the the Map Many types of layers ( ) Dim pMxDoc As IMxDocument Set pMxDoc = ThisDocument Dim pMap As IMap Set pMap = pMxDoc.FocusMap Dim pLayer As ILayer Set pLayer = pMap.Layer(1) Is pLayer a FeatureLayer? If TypeOf pLayer Is IFeatureLayer Then MsgBox Yes!, it’s a feature layer End If MxDocument Map FeatureLayer Layer * * Others A * OMD code example: Maps and layers In the example above, the object model diagram can be used as a guide for writing code. Your starting point for writing code in ArcMap is generally the ThisDocument preset variable. By consulting the ArcMap object model diagram, you would find that the IMxDocument interface on MxDocument (rather than the default IDocument interface to which ThisDocument points) has properties for accessing Maps (data frames). Because of the composed of relationship (?) shown in the diagram, and the multiplicity (*), you know that an MxDocument could potentially have several associated Maps. To insure that you get the Map that your user is currently working in, you use the FocusMap property. Looking at the diagram again, you notice that a Map is composed of (?) potentially several (*) Layers. From the Map, you can retrieve a Layer at a given index position (you are accessing the 2nd Layer in the code above). Finally, because Layer is an abstract class that has several subtypes (?), you would want