xcdatamodel的实质

修改后缀名为zip或者其它，可以查看到xcdatamodel是一个描述文件

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>

<model type="com.apple.IDECoreDataModeler.DataModel" documentVersion="1.0" lastSavedToolsVersion="12141" systemVersion="16G29" minimumToolsVersion="Xcode 7.3" sourceLanguage="Objective-C" userDefinedModelVersionIdentifier="">

    <entity name="Doogle" representedClassName="Doogle" syncable="YES">

        <attribute name="pexdeg" optional="YES" attributeType="String" syncable="YES"/>

    </entity>

    <entity name="Entity" syncable="YES"/>

    <entity name="GoooGoole" representedClassName="GoooGoole" syncable="YES">

        <attribute name="xxx" optional="YES" attributeType="String" syncable="YES"/>

    </entity>

    <elements>

        <element name="Doogle" positionX="18" positionY="72" width="128" height="60"/>

        <element name="Entity" positionX="-189" positionY="-162" width="128" height="45"/>

        <element name="GoooGoole" positionX="-396" positionY="-405" width="128" height="60"/>

    </elements>

</model>