IStreaming
stream of consciousness of an entrenched developer
Wednesday, September 14, 2016
Sunday, June 7, 2015
The Counted
http://www.theguardian.com/us-news/ng-interactive/2015/jun/01/the-counted-police-killings-us-database#
Wednesday, April 8, 2015
Saturday, November 22, 2014
Tuesday, March 18, 2014
Asynchronous Repository Pattern
I've been thinking a bit about network and other I/O latency problems and the traditional repository pattern. Started toying with the idea that a repository facade could explicitly expose a "promise-like" interface like the following.
public interface IRepository<T, in U> where T: class, new() where U: struct { Task<T> GetById(U id); Task<bool> Save(T entity); Task<bool> Remove(T entity); Task<IEnumerable<T>> GetAll(); }
Where T is the DTO and U is the underlying identifier type (int, Guid etc.)
This is all essentially client-side whereas the client is communicating with a resource (and perhaps resource is a better name than repository). So for instance, if I was communicating with a ReSTful service - my resource (or implementation of this particular pattern) could look something like the following.(This is currently implemented using RestSharp client using the ServiceStack.Text serializers)
Instantiating the implementation could be as simple as:public class RestfulClient<T, U> : RestClient, IRepository<T, U> where T: class, new() where U: struct { private readonly string _resource; private readonly ServiceStackJsonDeserializer deserializer; private readonly ServiceStackJsonSerializer serializer; private const string requestString = "application/json"; private const DataFormat requestFormat = DataFormat.Json; public RestfulClient(string baseUrl, string resource) : base(baseUrl) { this._resource = resource; this.deserializer = new ServiceStackJsonDeserializer(); this.serializer = new ServiceStackJsonSerializer(); ServiceStack.Text.JsConfig.EmitCamelCaseNames = true; this.AddHandler(requestString, new ServiceStackJsonDeserializer()); } private string UrlWithId(U id) { return string.Concat(this._resource, "/", id); } private RestRequest FormatRequest(string resource, Method method, T entity) { var req = new RestRequest(resource, method); if (entity != null) { req.RequestFormat = requestFormat; req.JsonSerializer = this.serializer; req.AddParameter(requestString, this.serializer.Serialize(entity), ParameterType.RequestBody); }; return req; } public Task<T> GetById(U id) { var t = Task.Factory.StartNew(() => this.deserializer.Deserialize<T>(this.ExecuteGetTaskAsync(FormatRequest(UrlWithId(id), Method.GET, null)).Result), CancellationToken.None); return t; } public Task<bool> Save(T entity) { var t = Task.Factory.StartNew(() => this.Execute(FormatRequest(this._resource, Method.POST, entity)).ResponseStatus == ResponseStatus.Completed, CancellationToken.None); return t; } public Task<bool> Remove(T entity) { var t = Task.Factory.StartNew(() => this.Execute(FormatRequest(this._resource, Method.DELETE, entity)).ResponseStatus == ResponseStatus.Completed, CancellationToken.None); return t; } public Task<IEnumerable<T>> GetAll() { var t = Task.Factory.StartNew(() => this.deserializer.Deserialize<IEnumerable<T>>(this.ExecuteTaskAsync(FormatRequest(this._resource, Method.GET, null)).Result), CancellationToken.None); return t; } }
var rc = new RestfulClient<ToDo, int>("http://localhost:53327", "api/v1/todos");Consuming looks like:
rc.GetById(id).ContinueWith((todo)=> Console.Write(todo.Result.Title));The nice thing is that the consuming client gets all the benefit of .ContinueWith (etc.) I'm not sure if I'm chasing dragons at this point - but I'm mulling it over...thoughts?
Monday, June 10, 2013
Adhering to the DRY Principal in Javascript/Knockout
One of the things that honestly "hurt my feelings" when developing an HTML5 replacement application awhile back - was that the ViewModel needed to be declared in multiple places. Once in the service and again in the client. Of course, all the demonstrations during tech-week seemed to gloss over this with very simplistic applications. Required reading - Pragmatic Principles
Now, there may be ample reason to want to do this -> what I'm enacting upon in the client may require a subset (possibly?) but I would contend that it should probably be a different service call. Don't transfer bytes that you don't need! So I created a static class helper to be used within a Razor template - and proceeded to forgot all about it.
A colleague from another department heard about/asked me about it and I rediscovered it. Enjoy. As always YMMV. If you improve on it - share it. I'll laud you copiously.
The helper:
The template:
Now, there may be ample reason to want to do this -> what I'm enacting upon in the client may require a subset (possibly?) but I would contend that it should probably be a different service call. Don't transfer bytes that you don't need! So I created a static class helper to be used within a Razor template - and proceeded to forgot all about it.
A colleague from another department heard about/asked me about it and I rediscovered it. Enjoy. As always YMMV. If you improve on it - share it. I'll laud you copiously.
The helper:
public static class HtmlHelper
{
private static string JavaScriptify(string s)
{
return string.Join(".", s.Split('.').Select(x => x[0].ToString().ToLower() + x.Substring(1, x.Length - 1)));
}
public static IHtmlString KnockoutFrom<T>(this HtmlHelper<T> html, T obj)
{
var serializer = new JsonSerializer
{
ContractResolver = new CamelCasePropertyNamesContractResolver()
};
var sb = new StringBuilder();
sb.Append("(function() {");
var json = JObject.FromObject(obj, serializer);
sb.Append("var vm = ko.mapping.fromJS(" + json + ");");
var type = obj.GetType();
var ns = JavaScriptify(type.Namespace);
sb.Append("namespace('" + ns + "');");
sb.Append(ns + "." + JavaScriptify(type.Name) + " = vm;");
sb.Append("})();");
return new HtmlString(sb.ToString());
}
}
The template:
@Html.KnockoutFrom(Model)
Friday, May 17, 2013
WSDL service returning DataSet? Seriously?
Just got a 'last-minute' TODO - have to establish another interface for state agency. Like any good developer - I grab the WSDL and 'prop-up' a test service. Imagine my surprise when I see the defined method results as DataSet. Yup. Can be anything - based on nature of the "select" - egads.
The ONLY reasonable - and its by NO MEANS reasonable - "theory" that *might* explain this 'design' decision is that auto-generated proxies won't 'break'. (Yea. It's a lame excuse and kinda defeats the purpose of contract-first development) Besides, auto-generated proxies are for the faint-hearted (HTTP/XML for me).
How to generically 'mock' a dataset? Grab NBuilder from NuGet and add to your project. Then add a POCO representation of the fields you wish to return. Then call this:
The ONLY reasonable - and its by NO MEANS reasonable - "theory" that *might* explain this 'design' decision is that auto-generated proxies won't 'break'. (Yea. It's a lame excuse and kinda defeats the purpose of contract-first development) Besides, auto-generated proxies are for the faint-hearted (HTTP/XML for me).
How to generically 'mock' a dataset? Grab NBuilder from NuGet and add to your project. Then add a POCO representation of the fields you wish to return. Then call this:
private static DataSet CreateDataSet<T>(int numberOfRows = 1) { var datatable = new DataTable(typeof (T).Name); typeof (T).GetProperties().ToList().ForEach( x => datatable.Columns.Add(x.Name)); Builder<T>.CreateListOfSize(numberOfRows).Build() .ToList().ForEach( x => datatable.LoadDataRow(x.GetType().GetProperties().Select( y => y.GetValue(x, null)).ToArray(), true)); var dataset = new DataSet(); dataset.Tables.Add(datatable); return dataset; }
soapUI tests against WSDL methods work - now 'back-to-work'!
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