5
我正在嘗試實現篩選器/管道模式，以便我可以接受輸入，通過多個篩選器處理它並在最後得到輸出。其中輸入/輸出類型對於每個篩選器不同的通用管道
當輸入類型和最終輸出類型相同並且每個篩選器也使用相同類型時，我可以輕鬆完成此操作。但是，我想輸入一個類型並獲得另一個類型。
例如 通過文件名獲取csvfile，將其加載到單個字符串中，解析它們，驗證並輸出爲xml。僞代碼示例：
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
這是我到目前爲止有：
IFilter, FilterBase, FilterImplementation
IPipeline, Pipeline
IBusinessObject, BusinessObject, BusinessObjectImplementation
我的目的是要能夠有IFilter<T,U>一個List，T and U are IBusinessObject
不過，我得到一個「嘗試將IFilter<IBusinessObject, IBusinessObject>添加到列表時，無法從BusinessObjectImplementation轉換爲IBusinessObject「。
Apols所有的代碼...它的最後一部分將不會編譯
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>());
}
}
唯一的例外是在.Register線之上
錯誤2參數1：不能從 '
BusinessLogic.FilterCsvFileLoader<BusinessObjects.FilenameObject,BusinessObjects.CSVFile>' 轉換爲 'BusinessLogic.IFilter<BusinessObjects.IBusinessObject,BusinessObjects.IBusinessObject>'
C：\用戶\ davidc \文檔\ Visual Studio 2010 \ Projects \ MPMeFeed \ TestConsole \ Program.cs 15 23 TestConsole
謝謝你，和一個很好的解釋，爲什麼這沒有奏效。 – BlueChippy