我正在尝试实现过滤器/管道模式,以便我可以获取输入,通过多个过滤器对其进行处理并在最后获得输出。
当输入类型和最终输出类型相同并且每个过滤器也使用相同类型时,我可以很容易地做到这一点。但是,我想输入一种类型并输出另一种类型。
例如 通过文件名获取 csv 文件,将其加载到单独的字符串中,解析它们,验证并输出为 xml。伪代码示例:
input = filename
filter = load csv file <filename, list<string>>
filter = parse csv <list<string>, list<businessobject>>
filter = validate objects <list<businessobject>, list<businessobject>> *... return type same as input type in this case.*
filter = create xml <list<businessobject>, XDocument>
filter = validate XDoc <XDocument, XDocument>
output = XDocument
这是我目前所拥有的:
IFilter, FilterBase, FilterImplementation
IPipeline, Pipeline
IBusinessObject, BusinessObject, BusinessObjectImplementation
我的意图是能够拥有 IFilter<T,U>
的列表其中 T and U are IBusinessObject
但是,我在尝试添加 BusinessObjectImplementation
时收到“无法从 IBusinessObject
转换为 IFilter<IBusinessObject, IBusinessObject>
”到列表中。
Apols 的所有代码...它的最后一部分不会编译
public interface IFilter<T, U>
where T : IBusinessObject
where U : IBusinessObject
{
U Execute(T input);
}
public abstract class FilterBase<T, U> : IFilter<T, U>
where T : IBusinessObject
where U : IBusinessObject, new()
{
protected abstract U Process(T input);
public U Execute(T input)
{
return Process(input);
}
}
public class FilterCsvFileLoader<T, U> : FilterBase<T, U>, IFilter<T, U>
where T : FilenameObject, IBusinessObject
where U : CSVFile, IBusinessObject, new()
{
public FilterCsvFileLoader()
{ }
protected override U Process(T input)
{
U result = new CSVFile(input) as U;
return result;
}
}
public interface IPipeline
{
IBusinessObject Execute(IBusinessObject input);
IPipeline Register(IFilter<IBusinessObject, IBusinessObject> filter);
}
public class Pipeline : IPipeline
{
private List<IFilter<IBusinessObject, IBusinessObject>> _filters = new List<IFilter<IBusinessObject, IBusinessObject>>();
public IBusinessObject Execute(IBusinessObject input)
{
var result = input;
foreach (var filter in _filters)
{
result = filter.Execute(result);
}
return result;
}
public IPipeline Register(IFilter<IBusinessObject, IBusinessObject> filter)
{
_filters.Add(filter);
return this;
}
}
public interface IBusinessObject
{
bool Validate();
List<string> ValidationErrors { get; }
}
public class BusinessObject : IBusinessObject
{
private List<BusinessRule> _businessRules = new List<BusinessRule>();
private List<string> _validationErrors = new List<string>();
public List<string> ValidationErrors
{
get { return _validationErrors; }
}
protected void AddRule(BusinessRule rule)
{
_businessRules.Add(rule);
}
public bool Validate()
{
bool isValid = true;
_validationErrors.Clear();
foreach (BusinessRule rule in _businessRules)
{
if (!rule.Validate(this))
{
isValid = false;
_validationErrors.Add(rule.ErrorMessage);
}
}
return isValid;
}
}
public class FilenameObject : BusinessObject, IBusinessObject
{
string _filename;
public string Filename
{
get { return _filename; }
}
public FilenameObject(string filename)
{
_filename = filename;
}
}
public class CSVFile : BusinessObject, IBusinessObject
{
private string _filename;
private string[] _splitChar = new string[] { "," };
public List<List<string>> Lines { get; set; }
public CSVFile()
{ }
public CSVFile(FilenameObject filename)
: this()
{
_filename = filename.Filename;
Lines = new List<List<string>>();
}
private void ImportFile()
{
FileInfo fi = new FileInfo(_filename);
using (StreamReader sr = new StreamReader(fi.Open(FileMode.Open, FileAccess.Read, FileShare.None)))
{
String readline;
while ((readline = sr.ReadLine()) != null)
{
var line = (from l in readline.Split(_splitChar, StringSplitOptions.None)
select l.Trim()).ToList();
Lines.Add(line);
}
}
}
}
class Program
{
static void Main(string[] args)
{
var pipeline = new Pipeline()
.Register(new FilterCsvFileLoader<FilenameObject, CSVFile>());
}
}
异常在上面的.Register行
Error 2 Argument 1: cannot convert from '
BusinessLogic.FilterCsvFileLoader<BusinessObjects.FilenameObject,BusinessObjects.CSVFile>
' to 'BusinessLogic.IFilter<BusinessObjects.IBusinessObject,BusinessObjects.IBusinessObject>
'
C:\Users\davidc\Documents\Visual Studio 2010\Projects\MPMeFeed\TestConsole\Program.cs 15 23 TestConsole
最佳答案
这里的问题是 FilterCsvFileLoader<FilenameObject, CSVFile>
工具 IFilter<FilenameObject, CSVFile>
这不是 IFilter<IBusinessObject, IBusinessObject>
的派生类型尽管 FilenameObject
& CSVFile
源自 IBusinessObject
.
这是一个常见的错误。
尝试这样的事情:
public interface IFilter
{
IBusinessObject Execute(IBusinessObject input);
}
public interface IFilter<T, U> : IFilter
where T : IBusinessObject
where U : IBusinessObject
{
U Execute(T input);
}
public abstract class FilterBase<T, U> : IFilter<T, U>
where T : IBusinessObject
where U : IBusinessObject, new()
{
protected abstract U Process(T input);
IBusinessObject IFilter.Execute(IBusinessObject input)
{
return this.Execute((T)input);
}
public U Execute(T input)
{
return Process(input);
}
}
public interface IPipeline
{
IBusinessObject Execute(IBusinessObject input);
IPipeline Register<T, U>(IFilter<T, U> filter)
where T : IBusinessObject
where U : IBusinessObject;
}
public class Pipeline : IPipeline
{
private List<IFilter> _filters = new List<IFilter>();
public IBusinessObject Execute(IBusinessObject input)
{
var result = input;
foreach (var filter in _filters)
{
result = filter.Execute(result);
}
return result;
}
public IPipeline Register<T, U>(IFilter<T, U> filter)
where T : IBusinessObject
where U : IBusinessObject
{
_filters.Add(filter);
return this;
}
}
关于c# - 每个过滤器的输入/输出类型不同的通用管道,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/8308155/