CodeSmith : Merge策略
2014-03-04 12:35 -夜 阅读(141) 评论(0) 编辑 收藏 举报CodeSmith支持如下三种“合并策略”：
不过这些策略主要是针对C#，VB这些支持Region的语言，对于其它语言可能就需要使用其它方法，比如自定义Merge策略，CodeSmith允许通过CodeSmith.Engine.IMergeStrategy 来扩展“合并”策略，本人推荐CodeSmith的一个原因就是CodeSmith提供了很多接口而不仅仅是一个工具，比如除了CodeSmith支持的属性，XML属性，你也可以通过 CodeSmith.CustomProperties来自定义属性种类，除了CodeSmith支持的数据源种类（MySQL，Oracle），你也可以通过自定义的Schema Provider 支持新的数据库类型或是其它数据类型。
InsertRegion策略
InsertRegion 顾名思义，就是在源码中定义一个Region，然后让CodeSmith自动生成的代码只插入到该区域，而在区域外的代码CodeSmith不会去碰它们，从而实现了自定义的代码和自动生成代码的合并。
PreserveRegion策略
PreserveRegion 是定义多个区域，然后通知CodeSmith保持这些区域代码不变，自动创建的代码添加到这些区域的外面，和InsertRegion作用相反。
下面还是借用CodeSmith 自带的Merge示例说明一下这两种策略的基本用法：
首先是InsertRegion策略，定义一个类文件InsertRegionSample.cs
public class InsertRegionsSample
{
public void SomeCustomMethod()
{
// This is my custom code that I want to preserve.
// I can make changes to it and my changes will
// not be overwritten.
}
#region Sample Generated Region
// This region generated by CodeSmith on Saturday, 12 January 2013
#endregion
}
<%@ Template Language="C#" TargetLanguage="C#" Description="Demonstrates using an InsertRegion merge strategy in C#." %> 然后通过CodeSmith项目为模板设置Merge策略：
选择InsertRegion策略， 然后设置要插入的RegionName。
生成后的代码如下：
public class InsertRegionsSample
{
public void SomeCustomMethod()
{
// This is my custom code that I want to preserve.
// I can make changes to it and my changes will
// not be overwritten.
}
#region Sample Generated Region
// This region generated by CodeSmith on Saturday, 12 January 2013
#endregion
}
可以看到CodeSmith只在Region 处插入代码，而该Region外的部分保持不变。
类似的PreserveRegions策略，代码和模板定义如下：
PreserveRegionsSample.cs
public class PreserveRegionsSample
{
#region "Custom Region 1"
// This is a place holder for your custom code.
// It must exist so that CodeSmith knows where
// to put the custom code that will be parsed
// from the target source file.
// The region name is used to match up the regions
// and determine where each region of custom code
// should be inserted into the merge result.
#endregion
public void SomeGeneratedMethod()
{
// This section and all other non-custom code
// regions will be overwritten during each
// template execution.
// Current Date: Saturday, 12 January 2013
}
#region "Custom Region 2"
// The contents of this region will also be preserved
// during generation.
#endregion
}
<%@ Template Language="C#" TargetLanguage="C#" Description="Demonstrates using a PreserveRegions merge strategy in C#." %>
public class PreserveRegionsSample
{
#region "Custom Region 1"
// This is a place holder for your custom code.
// It must exist so that CodeSmith knows where
// to put the custom code that will be parsed
// from the target source file.
// The region name is used to match up the regions
// and determine where each region of custom code
// should be inserted into the merge result.
#endregion
public void SomeGeneratedMethod()
{
// This section and all other non-custom code
// regions will be overwritten during each
// template execution.
// Current Date: <%= DateTime.Now.ToLongDateString() %>
}
#region "Custom Region 2"
// The contents of this region will also be preserved
// during generation.
#endregion
}
模板中也定义了两个区域，然后为该模板设置Merge策略，使用PreserveRegion时可能有多个Region需要保留，因此可以使用RegX来定义要保留的Region：
InsertClass 策略用在给以重载的代码中插入自动生成的代码,挺起来和InsertRegion功能很类似，的确也是如此，但InsertClass支持更多的配置，可以实现更加灵活和强大的功能。
它支持的配置有：
|
Language |
String, Required |
只支持VB和C# |
|---|---|---|
| ClassName | String, Required | 需插入代码的类名. |
| PreserveClassAttributes | Boolean, defaults to False | 是否保留类已有的Attributes，缺省CodeSmith替代类原来的Attributes |
| OnlyInsertMatchingClass | Boolean, defaults to False | 是否只插入匹配的类定义中 |
| MergeImports | Boolean, defaults to False | 是否合并Import语句 |
| NotFoundAction | Enum, defaults to None | 如果指定的类没找到后的行动，可以None,InsertAtBottom，InsertInParent几种选项 |
| NotFoundParent | String, no default | 如果指定NotFoundAction为InsertInParent对应的父类名称. |
比如使用如下配置：
Language: C#
ClassName: “Pet”
PreserveClassAttributes: True
OnlyInsertMatchingClass: True
MergeImports: True
现有类定义：
using System;
using System.ComponentModel.DataAnnotations;
namespace Petshop
{
[ScaffoldTable(true)]
public class Pet
{
public int Age { get; set; }
public string FirstName { get; set; }
public string LastName { get; set; }
}
}
using System;
using System.Text;
namespace Petshop
{
public class Pet
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName
{
get { return String.Format("{0} {1}", FirstName, LastName); }
}
}
}
using System;
using System.ComponentModel.DataAnnotations;
using System.Text;
namespace Petshop
{
[ScaffoldTable(true)]
public class Pet
{
public string FirstName { get; set; }
public string LastName { get; set; }
public string FullName
{
get { return String.Format("{0} {1}", FirstName, LastName); }
}
}
} 
