sometimes when I implement watch pattern in my directives in angular, I need to evaluate multiple values at once but want the watch pattern to trigger only once. Lately I found the watchGroup that I was hoping it would do exactly the mentioned behavior above but unfortunately it doesn't so I came up with this idea of hashing my values to in a watch using a function as a first parameter. So I was wondering is this a good idea? Is there pitfall in this pattern?
Assuming that foo and bar are values between 0-99.
$scope.$watch(function(){ return foo*100+bar}, function(){//This only triggers once!});
Thanks for the inputs.
Mark
have your tried $watchCollection(obj, listener)? this API can help you watch an array of values.
check out this
Related
Background:
I switched from a filter inside my ng-repeat to a filter that I call manually because the filtered objects were too big and too many, causing immense performance issues when the filter function was constantly called.
Now I have to change the architecture and the first problem I ran into is the following...
Problem:
A project might be changed when executing a process inside of a different controller so I need to execute the filter function (getProjects) again after that.
I thought about moving the filter function to a Service class, in order to be able to call it from different controllers. But the problem then is, that I need the search field value (searchText) as parameter of the filter function - but that field is only accessible inside of the original controller.
I'm looking for an "clean" solution here - e.g. turning the searchfield into some kind of global rootscope variable doesn't sound right to me...but feel free to give me your opinion on how this is best solved.
Here's a minified example:
https://jsfiddle.net/wba2s4ey/
I already moved the filter function to the Service Class but I don't know how to pass the query value from the second controller and I don't think that's very clean.
This is how I solved it: https://jsfiddle.net/9j7stgo6/
I just think it's ugly that I have to directly use the Service inside of the html but I can't think of a better way. I previously tried declaring this.updateFilter = this.HelperService.updateFilter; in the ControllerOne, but it doesn't have the correct this then and can't find the method updateProjects.
I have some data on a model that comes in the form of a code such as "US60" and "US70".
I need to take that value and show a display value such as "US 7day/60hour" and "US 8day/70hour". I'm not sure if there is any best practices way to do this in Angular, and I'm not having much luck googling it.
What I would do is have a service that I pass in type and value, and it would return a display value, but as with many things in Angular, since this is my first Angular project, I don't know if it's a good way to do it or not.
I'm just needing to use the display value in html such as {{settings.cycle}} I am already able to access the variable, but I want to show the display value, not the actual value.
If I am getting the gist of your question correctly, you have the value available but want to alter how it is displayed on screen right?
There are two main approaches to do this in Angular, using a directive or a filter.
A filter is basically like a pipe in Unix. You can alter a value before it is being displayed. For example:
{ username | uppercase } will transform the username into an all-caps username. Naturally, you can define your own filters for your use case. Filters are mostly used to transform single values. So for your case, a filter sounds best.
A directive is commonly used to create entire components on a page. For example: <user-profile-card></user-profile-card> would be transformed, using the directive, into the appropriate html/css/logic. So these are used often for larger transformations which involve logic, like server requests. Still these directives could also be used for very small components.
So for your case, although what you are actually want to do is not completely clear to me honestly, a filter seems to be your best shot ;)
JS Bin here
This article describes a clever way to see if your (pure Angular) form model has changed since the initial load. In my mind it's a more accurate test of $dirty/$pristine. This allows us to do things like hide the "Save" button for a form if the model hasn't changed, even if the user has typed then deleted text.
So the question is, how can we do this with angular-formly? My hunch is that onChange for each field might be a good starting point, but I'm having a lot of trouble putting together the rest of the solution.
Hope the question makes sense. Any ideas would be very welcome. Thanks!
This might work in a limited capacity:
scope.initialValue;
var listener = scope.$watch(function(oldVal,newVal){
scope.initialValue = oldVal
listener();
})
atinder was correct in that the pure Angular approach actually works fine with angular-formly. I've created a working JS Bin here.
im looking to implement a directive to display status messages in my ionic angular app.. the idea is that i define a bunch of standard status messages in my template as follows and it's inspired by the stock ng-switch directive..
<status-bar code="statusCode" onShow="onStatusShow" onHide="onStatusHide">
<status-message when-code="OK" style="calm" timeout="3000">My HTML message</status-message>
...
...
<status-message when-complex style-field="style" text-field="text" timeout-field="timeout" />
</status-bar>
my requirements are these:
status-bar
the directive should bind to $scope.statusCode and depending upon its string value, it should activate one of the sub-directives except the when-complex one..
however, if i assign an object to $scope.statusCode, it should activate the when-complex directive if defined..
the directive also exposes an onShow and onHide callbacks..
when changing the value of $scope.statusCode, the previously active sub-directive should be completely hidden before showing the newly active one.. (animations)
status-message
style and timeout attributes are optional and will default to 'stable' and null respectively..
the timeout attribute will cause this sub-directive to show for a short time before clearing $scope.statusCode..
whereas i can write very simple directives, this one is proving to be a bit beyond me.. ive seen the source of ng-switch and its confusing.. i have tried myself as well but i havent gotten really far with this no matter how much ive tried.. im not posting my code approaches here not for the lack of trying but for the sake of cluttering and relevance..
so i was wondering if maybe someone could come up with a possible basic approach on codepen or plunkr that i can use as a base for expanding upon (since this is just a simplified explanation of what i intend to do with this directive).. or atleast point in the directions i need to go in..
after a night of brain-storming and coding punctuated by coffee and smoke breaks.. ive managed to make it work.. once again keeping ng-switch as a base.. the code is a bit long.. and i changed a few requirements along the way for better usability.. and some requirements like #2 and #3 dont work yet.. but im pretty sure ill make it work as well..
so if anybody is having a similar issue or is interested in my solution.. i can post it here.. :)
I've created a directive that wraps a text input field. One of the things I plan to embed in this directive is the validation behavior when it is required, but I'm stuck on one point. You are supposed to be able to refer to the validation errors for an input field using myForm.myField.$error or myForm[myField].$error. However, because my input is created by my directive, it shows up as myForm["{{myDirectiveName"].$error. This is unacceptable because I will have many such fields and I need to distinguish between them.
Plunkr that illustrates this.
The key line that causes problems is this:
console.log( !! form["{{htTextField}}"].$error.required);
What I expect to be able to write is:
console.log( !! form[attrs.htTextField].$error.required);
Many thanks for any help.
I ended up solving this by implementing my own required directive, borrowed from angular's, and customized to modify my own scope variables. Perhaps what I observed in my question is a bug, but I'm not expert enough to fix it in angular's code.