The Overflow Blog The global idea of what I'm trying to do is setting a class on the header depending on the current state of the application.Thanks for contributing an answer to Stack Overflow!
your coworkers to find and share information. An Angular app contains a tree of Angular components. One of the Angular core concepts is the update of a component’s DOM in case the framework detects changes in its fields used in the template binding expressions.
To persist the state of the Kendo UI Grid for Angular, use either of the following approaches: Use the dedicated methods; Handle the events of the Grid; Using Dedicated Methods. As my component never had a controller, I haven't thought to create one just to pass that $state :) In the other words it is possible to determine functions whose arguments will be some state fields and results will correspond with the values of other fields (supposed to be present in accordance with the component’s logic).If such functions cannot be determined that simply means the absence of logic which happens when the component is only used for data presentation.To explain the idea let’s consider a simple component “Calculator”. Eventually though, all the fields become consistent again (except for the situations with infinite loops which should be considered as bugs) and keep being consistent until a new event happens.Considering that the only way to make changes in the component’s state is to create a new state instance the reaction on an event can be represented as follows:Let’s take a closer look at the situation when a user changes the input field:As shown above, there is always a transition function between a previous state and the next one (the function can be compound). A component must belong to an NgModule in order for it to be available to another component or application. This is a special use case for stateless components that have a function inside to capture UI state and do something with it. The role this component plays is to capture the label of a new todo item, which is illustrated inside the submit function.
Stack Overflow works best with JavaScript enabled At the same time, Angular leaves the way of how the component’s fields are updated to a developer and that works well in some simple scenarios since developers can quickly create components which meet all necessary requirements without the need to introduce any additional abstractions. In Angular it can be implemented as follows: almost all of the component fields need to be moved into a separate class and only one field left in the component — it is “state” whose type will be that separate class. To access the current Grid state, use a component field in the respective State object. That can be fixed by explicit change detection when a new consistent state is applied. It can be implemented “manually” but there are several tasks that cannot be easily done in Angular without external libraries:1) Mapping state fields to Input/Output parameters of Angular componentLet us look how the calculator can be implemented using the library.First, we need to create a separate class which will represent the component state:Then the state should be assigned to an Angular component using inheritance from The methods can be called from markup (the AoT compilation will check their signatures) to move the component to a new state:The reaction on input change is more complex and that is why it was moved to a separate method:Now we are ready to create transition functions which will be called when the text fields are changed:Our component does not look not very useful without any Input/Output parameters, so let’s mark some fields as component Input/Output:The only thing is left — when arguments are updated form outside (via input parameters) the text in input fields should also be be updated:The calculator works now, but let’s add some cool thing to it, for example debouncing on user input:It is very simple but now there is problem — state changing happens out of the angular zone and it cannot detect the changes anymore. UI component infrastructure and Material Design components for mobile and desktop Angular web applications. There is good way to do that — we just need to add the second component instance and bind all its Input/Output properties to the original one:I have been using the approach described in the article for the last year, and it proved very helpful when I needed to develop some complex components. Private self-hosted questions and answers for your enterpriseProgramming and related technical career opportunitiesThat's right, thanks! It has two inputs for arguments and selector of arithmetic operations:Arguments and operator can be selected by user or set through component input parameters. To do that we need to add an implementation of onAfterStateApplied() to the component class:Here we also can show that Angular change detection can be entirely disabled for the component:Now it is completed, but let’s test that Input/Output works correctly. By using our site, you acknowledge that you have read and understand our Unlike other directives, only one component can be instantiated per an element in a template. For example (i'm using ES2015 here and follow Todd Motto's Angular Styleguide ): It is focused on the events distributed over time, but in the majority of cases an immediate reaction to an occurring event is required, and there is another approach (for example used in React) which provides more elegant solution for the above described problem.The idea of this approach is to separate the component and its data into two different types. However, in more complex scenarios, it becomes obvious that the lack of restrictions on the component’s data changes, turns into a problem due to the increased number of side effects which makes the behavior of components less predictable.There are also additional factors affecting the difficulty of maintaining a free-changing state:When a component is executing one or several asynchronous operations this means that there are several logical flows changing the shared state, and some synchronization efforts are required. However, these new changes also could lead to inconsistency and further changes will continue happening. This component also doesn’t receive any data via property binding, and that’s perfectly acceptable.