![]() ![]() For example, that hypothetical application might have a table view to display the available teams, and the data wouldn't need to be pulled until that table view is loaded for the first time. We simply declare how the data is related, and then PLRelational takes care of efficiently loading and transforming the data as it is needed. Note that in these examples, we're not actually forcing any data to load. Use `difference` to determine which teams are available to join Let selectedEmployeeTeams = employeeTeams We can use relational algebra to find out which teams a certain employee hasn't yet joined: // Figure out which teams the employee *has* already joined Or suppose we are building an application to manage the company's sports teams. max, count) and other operations like leftOuterJoin that are considered extensions to the relational algebra.įor example, we can find the number of employees in the HR department that like chocolate ice cream: let chocoholicsInHR = employees. PLRelational includes a full set of combinators, including aggregate functions (e.g. join and select) that are familiar if you've spent time with SQL. In the above example, we used some basic relational algebra operations (e.g. Once the update is processed, our observer will see the change will be delivered on the main queue when ready.) (Async updates and queries are processed in the background results Update all employees in the HR department to have the name LindaĪllEmployees.asyncUpdate(Dept.name *= "HR", ) changes, extract the changed name and append to `empThreeNames`. ![]() Observe changes made to Cathy's record. Perhaps some example code can help explain what that all means: // Use combinators to `join` our two on-disk relations and `project` observe fine-grained deltas when a relation's data has changed.asynchronously query and update those relations.declaratively express relationships using relational algebra.At its core, PLRelational is a Swift framework that allows you to: PLRelational is our (exploratory) answer to that question. A question then emerged: can we build a library that allows us to express those transformations in a concise way, with an eye towards simplifying app development? It sounds so simple when boiled down like that, but the reality of app development is a different story, often filled with twisty, error-prone UI code, even with the help of functional programming aids (e.g. While working on the next major version of VoodooPad, an observation was made: user interfaces are basically just bidirectional transformation functions, taking data from some source and presenting it to the user, and vice versa. Since the last time I've run this I upgraded to Mountain Lion and Xcode 4.5.Reactive Relational Programming with PLRelational This exact HTML used to work just fine with hiutil. The first part of every file is basically the same: Line 14, column 8 is the closing of the head tag. These errors are repeated for every single file. Index.html - Parse error: Error 76, Description: (null), Line: 14, Column: 8 Index.html - Parse error: The operation couldn’t be completed. When I run hiutil on the html exported from Voodoopad, I get a bunch of errors: Zach-iMac:Desktop zach$ hiutil -a -create Help/ -file Help/Help.helpindex -1 -vvv The Voodoopad doc is set to run hiutil to create the help index when it exports.Īfter noticing that many of my help anchors weren't working, I traced it back to hiutil. Basically I have a Run Script build phase which tells Voodoopad to export my document as html. I use Voodoopad to create my help docs, as described here. ![]()
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