What is the kotlin way of accomplisg this:
public static TreeMap<Integer, ArrayList<HomeItem>> getHomeItemListsSeparatedByPageId(List<HomeItem> homeItemsList) {
if (homeItemsList.size() == 0) {
return new TreeMap<>();
}
TreeMap<Integer, ArrayList<HomeItem>> map = new TreeMap<>();
for (HomeItem hl : homeItemsList) {
if (map.get(hl.getVisiblePageId()) == null) {
map.put(hl.getVisiblePageId(), new ArrayList<>());
}
map.get(hl.getVisiblePageId()).add(hl);
}
return map;
}
I have tried to apply groupBy on my args list but it returns an HashMap.
EDIT: Basically, the original list is queried, and it is grouped by visiblePageId, and added to a treemap whose key is the id and the value are the items with that id
You can use the groupByTo method and pass a TreeMap instance as the first argument.
fun getHomeItemListsSeparatedByPageId(homeItems: List<HomeItem>) =
homeItems.groupByTo(TreeMap()) { it.visiblePageId }
Related
I am writing and extension for OpenXML like shown in the sample. I would like to avoid having to pass the WorkbookPart as parameter. Is there any way to get the WorkbookPart directly from the row?
public static string GetCellTextValue(this Row row, WorkbookPart workbookPart, string column)
{
var cells = row.Elements<Cell>();
var cell = cells.Where(p => p.CellReference == column + row.RowIndex.ToString()).FirstOrDefault();
if (cell.DataType != null)
{
if (cell.DataType == CellValues.SharedString)
{
int id = -1;
if (Int32.TryParse(cell.InnerText, out id))
{
SharedStringItem item = workbookPart.SharedStringTablePart.SharedStringTable.Elements<SharedStringItem>().ElementAt(id);
if (item.Text != null)
{
return item.Text.Text;
}
else if (item.InnerText != null)
{
return item.InnerText;
}
else if (item.InnerXml != null)
{
return item.InnerXml;
}
}
}
}
return string.Empty;
}
Unfortunately, none of the strongly-typed classes of the Open XML SDK (e.g., Workbook, Worksheet, Row) have properties pointing back to the OpenXmlPart (e.g., WorkbookPart, WorksheetPart) in which they are contained or any other part related to their immediate container. Unless you amend your API in other ways, you will have to pass that WorkbookPart.
I am currently implementing a RESTFUL API that provides endpoints to interface with a database .
I want to implement filtering in my API , but I need to provide an endpoint that can provide a way to apply filtering on a table using all the table's columns.
I've found some patterns such as :
GET /api/ressource?param1=value1,param2=value2...paramN=valueN
param1,param2...param N being my table columns and the values.
I've also found another pattern that consists of send a JSON object that represents the query .
To filter on a field, simply add that field and its value to the query :
GET /app/items
{
"items": [
{
"param1": "value1",
"param2": "value",
"param N": "value N"
}
]
}
I'm looking for the best practice to achieve this .
I'm using EF Core with ASP.NET Core for implementing this.
Firstly be cautious about filtering on everything/anything. Base the available filters on what users will need and expand from that depending on demand. Less code to write, less complexity, fewer indexes needed on the DB side, better performance.
That said, the approach I use for pages that have a significant number of filters is to use an enumeration server side where my criteria fields are passed back their enumeration value (number) to provide on the request. So a filter field would comprise of a name, default or applicable values, and an enumeration value to use when passing an entered or selected value back to the search. The requesting code creates a JSON object with the applied filters and Base64's it to send in the request:
I.e.
{
p1: "Jake",
p2: "8"
}
The query string looks like:
.../api/customer/search?filters=XHgde0023GRw....
On the server side I extract the Base64 then parse it as a Dictionary<string,string> to feed to the filter parsing. For example given that the criteria was for searching for a child using name and age:
// this is the search filter keys, these (int) values are passed to the search client for each filter field.
public enum FilterKeys
{
None = 0,
Name,
Age,
ParentName
}
public JsonResult Search(string filters)
{
string filterJson = Encoding.UTF8.GetString(Convert.FromBase64String(filters));
var filterData = JsonConvert.DeserializeObject<Dictionary<string, string>>(filterJson);
using (var context = new TestDbContext())
{
var query = context.Children.AsQueryable();
foreach (var filter in filterData)
query = filterChildren(query, filter.Key, filter.Value);
var results = query.ToList(); //example fetch.
// TODO: Get the results, package up view models, and return...
}
}
private IQueryable<Child> filterChildren(IQueryable<Child> query, string key, string value)
{
var filterKey = parseFilterKey(key);
if (filterKey == FilterKeys.None)
return query;
switch (filterKey)
{
case FilterKeys.Name:
query = query.Where(x => x.Name == value);
break;
case FilterKeys.Age:
DateTime birthDateStart = DateTime.Today.AddYears((int.Parse(value) + 1) * -1);
DateTime birthDateEnd = birthDateStart.AddYears(1);
query = query.Where(x => x.BirthDate <= birthDateEnd && x.BirthDate >= birthDateStart);
break;
}
return query;
}
private FilterKeys parseFilterKey(string key)
{
FilterKeys filterKey = FilterKeys.None;
Enum.TryParse(key.Substring(1), out filterKey);
return filterKey;
}
You can use strings and constants to avoid the enum parsing, however I find enums are readable and keep the sent payload a little more compact. The above is a simplified example and obviously needs error checking. The implementation code for complex filter conditions such as the age to birth date above would better be suited as a separate method, but it should give you some ideas. You can search for children by name, and/or age, and/or parent's name for example.
I have invented and found it useful to combine a few filters into one type for example CommonFilters and make this type parseable from string:
[TypeConverter(typeof(CommonFiltersTypeConverter))]
public class CommonFilters
{
public PageOptions PageOptions { get; set; }
public Range<decimal> Amount { get; set; }
//... other filters
[JsonIgnore]
public bool HasAny => Amount.HasValue || PageOptions!=null;
public static bool TryParse(string str, out CommonFilters result)
{
result = new CommonFilters();
if (string.IsNullOrEmpty(str))
return false;
var parts = str.Split(new[] { ' ', ';' }, StringSplitOptions.RemoveEmptyEntries);
foreach (var part in parts)
{
if (part.StartsWith("amount:") && Range<decimal>.TryParse(part.Substring(7), out Range<decimal> amount))
{
result.Amount = amount;
continue;
}
if (part.StartsWith("page-options:") && PageOptions.TryParse(part.Substring(13), out PageOptions pageOptions))
{
result.PageOptions = pageOptions;
continue;
}
//etc.
}
return result.HasAny;
}
public static implicit operator CommonFilters(string str)
{
if (TryParse(str, out CommonFilters res))
return res;
return null;
}
}
public class CommonFiltersTypeConverter : TypeConverter
{
public override bool CanConvertFrom(ITypeDescriptorContext context, Type sourceType)
{
if (sourceType == typeof(string))
{
return true;
}
return base.CanConvertFrom(context, sourceType);
}
public override object ConvertFrom(ITypeDescriptorContext context,
CultureInfo culture, object value)
{
if (value is string str)
{
if (CommonFilters.TryParse(str, out CommonFilters obj))
{
return obj;
}
}
return base.ConvertFrom(context, culture, value);
}
}
the request looks like this:
public class GetOrdersRequest
{
[DefaultValue("page-options:50;amount:0.001-1000;min-qty:10")]
public CommonFilters Filters { get; set; }
//...other stuff
}
In this way you reduce the number of input request parameters, especially when some queries don't care about all filters
If you use swagger map this type as string:
c.MapTypeAsString<CommonFilters>();
public static void MapTypeAsString<T>(this SwaggerGenOptions swaggerGenOptions)
{
swaggerGenOptions.MapType(typeof(T), () => new OpenApiSchema(){Type = "string"});
}
I have 3 methods these are same methods only some parameters will be change I want to write one method how can i write
public string method1(int id)
{
var getAllStudents = rep.Students.Where(e => e.StudentId == id).ToList();
foreach (var item in getAllStudents)
{
if (item.isActive != true)
return "Error";
}
return "OK";
}
public string method2(int id)
{
var getAllTeachers = rep.Teachers.Where(e => e.TeacherId == id).ToList();
foreach (var item in getAllTeachers)
{
if (item.isActive != true)
return "Error";
}
return "OK";
}
public string method3(int id)
{
var getAllClasses = rep.Classes.Where(e => e.ClassId == id).ToList();
foreach (var item in getAllClasses)
{
if (item.isActive != true)
return "Error";
}
return "OK";
}
I think there is very easy way to write 1 method. the think is where parameter has different id..
Thanks.
Avoid conditional logic based on arguments. This leads to fragile code because every parameter combination has to be tested to be considered reliable. This leads to complex code that is easily prone to bugs. Having simpler single-purpose methods are typically much more reliable and easier to understand and maintain.
For instance given your example and assuming that "rep" was your instance's DbContext...
public bool IsActiveStudent(int id)
{
bool result = rep.Students.Any(x => x.StudentId == id && x.IsActive);
return result;
}
public bool IsActiveTeacher(int id)
{
bool result = rep.Teachers.Any(x => x.TeacherId == id && x.IsActive);
return result;
}
public bool IsActiveClass(int id)
{
bool result = rep.Classes.Any(x => x.ClassId == id && x.IsActive);
return result;
}
These can be essentially one-liners by simply returning the .Any() result. I tend to favour selecting the result into a variable first and returning it on a separate line since it makes it easier to breakpoint and inspect.
If you need to return a string for "Ok" vs. "Error" then:
return result ? "OK" : "Error";
Methods should strive to do one thing, and do it well. Easy to understand and troubleshoot if need be. Adding parameters and conditional code inside the method merely makes the code more volatile and leaves openings for bugs. In the end it doesn't make the code much shorter when the initial method could be simplified.
You can not overload methods if they signatures are the same.
You have two methods with the same signature:
public string checkexist(int id)
What you can do is to rename your methods, like this:
public interface WriteSomethingHere {
public boolean isStudentExist(int id);
public boolean isTeacherExist(int id);
public boolean isClassExist(int id);
}
I just found answer using generic repo
public T GetEntity<T>(int Id)
where T : class
{
using (MyEntities rpContext = new MyEntities())
{
return rpContext.Set<T>().Find(e => e.Id == Id);
}
}
after calling
var entityStudent = GetEntity<Student>(1);
var entityTeacher = GetEntity<Teacher>(1);
var entityClasses = GetEntity<Classes>(1);
You have Create Enumeration
Public Enum ParameterStaus:short
{
Student=1,
Teacher=2,
Classess=3
}
public string method2(int id.ParameterStatus status)
{
if(status==ParameterStatus.Teacher)
{
var getAllTeachers = rep.Teachers.Where(e => e.TeacherId == id).ToList();
foreach (var item in getAllTeachers )
{
if (item.isActive != true)
return "Error";
}
return "OK";
}
}
Else if(status==ParameterStatus.Student)
{
var getAllStudents = rep.Students.Where(e => e.StudentId == id).ToList();
foreach (var item in getAllStudents)
{
if (item.isActive != true)
return "Error";
}
return "OK";
}
Else
{
var getAllClasses = rep.Classes.Where(e => e.ClassId == id).ToList();
foreach (var item in getAllClasses)
{
if (item.isActive != true)
return "Error";
}
return "OK";
}
}
The Plan:
So now what I basically want is to take my propertys out of the class, let the user pick some and then pull a List with ONLY those propertys out of MongoDB.
The Code:
here is where the method starts:
private void DoStuffExecute(object obj)
{
Class class= new Class();
ExtractClass(class);
if (propList != null)
{
var result = classService.DoStuff(propList);
}
}
in "ExtractClass()" the Propertys are being pulled out of the Class.
void ExtractClass(object obj)
{
foreach (var item in obj.GetType().GetProperties())
{
propList.Add(item.Name);
}
}
and finally in "classService.DoStuff()" i try to set the "fields".
public List<class> DoStuff(List<string> Props)
{
try
{
var filter = Builders<class>.Filter.Empty;
var fields = Builders<class>.Projection.Include(x => x.ID);
foreach (var item in Props)
{
string str = "x.";
str += item.ToString();
fields = Builders<class>.Projection.Include(x => str);
fields = Builders<class>.Projection.Include(x => item);
}
var result = MongoConnectionHandler.MongoCollection.Find(filter).Project<class>(fields).ToList();
return result;
}
catch (Exception ex)
{
MessageBox.Show(ex.Message);
var result = new List<class>();
return result;
}
}
when i run the programm it gives me an "Unable to determine the serialization information for x=> value"... since im giving it a string.
The Question:
Does anyone have an Idea how to repair the code above or even make the plan work in another way?
thank you.
First of all: you are using such code lines as : var filter = Builders<class>.Filter.Empty; It is not possible, because class is a reserved keyword in c# (https://msdn.microsoft.com/en-us/library/x53a06bb.aspx) I assume, it's your Model, and i will speak about it as about Model class.
Include Filter needs Expression as a parameter, not a string, you should construct is as a expression. That's the second thing. Third, you should combine your includes as a chain, So your part of creating Include Filter from string List should look like:
var filter = Builders<Model>.Filter.Empty;
var fields = Builders<Model>.Projection.Include(x => x.Id);
foreach (var item in Props)
{
var par = Expression.Parameter(typeof(Model));
var prop = Expression.Property(par, item);
var cast = Expression.Convert(prop, typeof(object));
var lambda = Expression.Lambda(cast, par);
fields = fields.Include((Expression<Func<Model, object>>)lambda);
}
I have all expresiions separate for better understanding: first you create Parameter (x=>), than you add property (x=>x.Property1), than you should cast it to object, and after all create Lambda Expression from it.
And now the last part: You don't need all of it, Include function could get jsut a string as a parameter. So you could instead of all expression call write this:
fields = fields.Include(item);
I Use entity Framework 4.
I would like to be able to create a function that return an Expression func that will be use in a lambda expression.
var ViewModel = _db.Suppliers.Select(model => new {
model,SupType = model.SupplierType.SupplierTypeTexts.Where( st => st.LangID == 1)
});
I would like to make this call like that
var ViewModel = _db.Suppliers.Select(model => new {
model,SupType = model.SupplierType.GetText()
});
My Partial class is:
public partial class SupplierType
{
public Expression<Func<SupplierTypeText, bool>> GetText()
{
return p => p.LangID == 1;
}
How can i perform this.
Easy. For example, Let's assume you have a Product table that is mapped to Products EntitySet in your context, now you want to pass a predicate and select a Product:
Expression<Func<Product, bool>> GetPredicate(int id) {
return (p => p.ProductID == id);
}
You can call GetPredicate() with a Product ID to filter based on that:
var query = ctx.Products.Where(GetPredicate(1)).First();
The point really is that you can always pass a Lambda Expression to where an Expression<T> is needed.
EDIT:
You should change your code like this:
var ViewModel = _db.Suppliers.Select(model => new {
model,
SupType = model.SupplierType.SupplierTypeTexts.Where(GetText())
});
public Expression<Func<SupplierTypeText, bool>> GetText() {
return (stt => stt.LangID == 1);
}
If you want to dynamically create compiled Expression at runtime (as opposed to ones hardcoded against a particular data model at compile time) you need to use the static methods on the Expression class.