我提出的过滤设计充其量是笨拙的,最坏的情况是错误的。这个想法是有一个基类来支持选择列表,并让子类根据需要添加额外的过滤逻辑。
令我特别困惑的是如何在各种过滤条件更改时触发视图进行过滤(请参阅下面的 _ApplyFiler())。以这种方式设置过滤器是否合适?过滤后我应该在哪里取消订阅/将其设置为 null?
干杯,贝里尔
丑陋的代码:
public class SubjectPickerBase<T> : ViewModelBase, ISubjectPicker<T>
where T : class, IAvailableItem, INotifyPropertyChanged, IActivitySubject
{
public CollectionViewSource Subjects { get; private set; }
protected SubjectPickerBase() { }
protected void _Initialize(IEnumerable<T> subjects, string subjectName) {
...
Subjects = new CollectionViewSource { Source = subjects };
_ApplyFilter();
}
protected void _ApplyFilter() {
Subjects.View.Filter += Filter;
}
private bool Filter(object obj)
{
var subject = obj as T;
if (ReferenceEquals(subject, null)) return false;
NotifyPropertyChanged(() => Status);
var isIncludedBySubclass = OnFilter(subject);
var isIncludedByBase = subject.IsAvailable;
return isIncludedByBase & isIncludedBySubclass;
}
/// <summary>Hook to allow implementing subclass to provide it's own filter logic</summary>
protected virtual bool OnFilter(T subject) { return true; }
}
public class ProjectSelectionViewModel : SubjectPickerBase<ProjectViewModel>
{
public ProjectSelectionViewModel(IEnumerable<ProjectViewModel> projects)
{
...
_Initialize(projects, Strings.ActivitySubject__Project);
}
public string DescriptionMatchText {
get { return _descriptionMatchText; }
set {
ApplyPropertyChange<ProjectSelectionViewModel, string>(ref _descriptionMatchText, x => x.DescriptionMatchText, value);
_ApplyFilter();
}
}
private string _descriptionMatchText;
protected override bool OnFilter(ProjectViewModel subject)
{
...
var isDescriptionMatch = subject.IsMatch_Description(DescriptionMatchText);
return isPrefixMatch && isMidfixMatch && isSequenceNumberMatch && isDescriptionMatch;
}
}