I have an object that was created with GetxController and it has a list field. I want to select a specific item in that list and change some parameters. But I should be able to cancel this changing scenario. Because when I select an item and change it, also change that class list item.
In Dart, objects pass by reference. But I need to pass it by value for canceling change. There's any way to pass an object instance by value?
In this kind of scenario, you should try to use immutable types.
There are good Dart libraries for that, even if the language doesn't have native support for it... with truly immutable data types, you essentially get pass-by-value semantics. They also make it easy to make copies of your data with small modifications on the returned value (while the original obviously remains unmodified).
Example packages you could use:
built_collection
built_value
freezed
No.
But you can just make a copy yourself and pass that. And depending on whether the change was confirmed you can eiter copy it back into your list or not.
Related
I have a list of objects that need to be loaded into my app. But the load order matters. I’ve created a var which is a part of each object that indicates the load order where the lowest number gets loaded in first. Then I’ve set the default to be 9999. I can manually set this value on each object and override the default. Currently this is where I’m at.
Should I add more objects which need to be loaded in a specific order in the future, I want to make sure there are no conflicts. It seems to me like I could do that by making each load order number on the objects unique, (i.e. no duplicate numbers in all the load order variables).
Is there a way I can make Xcode throw an error or warning if it detects that anything conforming to a protocol has the same value on a variable from that protocol as any of the other conforming objects?
Well, you could list all the objects in an array literal in the order you want them loaded, and forgo the load order property entirely:
let objectsToLoad = [
ObjectDescriptor("hello"),
ObjectDescriptor("world"),
]
But if you have objects defined in disparate places and don't want a single unified array literal that lists them all, then I don't think you can get help from the compiler (or the linker).
In a few months, when Swift will have macros, you'll probably be able to get help from the compiler or the linker. The strategy is to use a macro to wrap each load-order constant in a macro that also generates some type definition whose name includes the constant, e.g. enum _LoadOrder_1 {}, enum _LoadOrder_357 {}, etc. Then, if you have a duplicate, either the compiler or the linker will fail due to the multiple definitions for a single identifier.
One person in Stackover Flow gave me a hint about creating a learning page.
Using the list, save the necessary data, id and favorite variables, and call them to the index number.
I was creating a class to implement it.
However, I realized that variables could not be stored in the list...
Is there a way to save it?
And I don't make a separate class, but I'm going to make a list in the file with the following code.
But before, I heard that using global variables makes me stutter and it's bad for memory.
Shall we use "const"?
If not, wouldn't it be a problem how to make the class?
Of course, favorite variables cannot be used because they change from time to time.
const List<Function> fav_1 = [favoriteButton_0_01_01,.....];
Is it okay to use only the const list as a global variable instead of making a class?
Can I put variables in the list? Then, how?
You can only put items with a matching type in the list.
if you define a list like "List" than only functions can be saved there.
if you define a list like "List" than only Integers can be saved there.
using const as a modifier will result in an unmodifiable list and so you won't be able to put anything in there.
I'm thinking of creating a VSCode extension to help people use a library I am creating. I've looked in 50 places and can only see documentation on getting the plain text of the document in which the completion suggestions are triggered.
My library exposes a function with two parameters, both objects with the same keys, but the first one will be defined already and the 2nd one will be passed in as an object literal. For example
const obj1 = {a:1, b:2};
doLibraryThing(obj1, {a:[], b:[]});
I want to provide code completion, or a snippet, or anything that can detect that doLibraryThing is being called, and know what properties were defined in obj1, even though usually it will be imported from another file; and then use those properties to generate the suggestion with the same properties, {a:[], b:[]}.
Is this possible?
I'm building a class (sorry - Agent) that will work with a set of Tank objects (Fluid Library) - doing things like monitoring individual levels or total level of all tanks, reporting on levels and initiating actions based on levels - things of that nature. For argument's sake let's call it a "TankMonitor" agent.
Ideally I'd like to be able to define a Parameter in my "TankMonitor" agent that allows me to define the tanks of interest when I place a TankMonitor in main. I have tried to define the type of the parameter as Other - ArrayList<Tank> however I don't know how to set up the next step to allow me to populate the ArrayList of Tanks when I put an instance of this agent in main. My preference would be to have a list type control to populate the ArrayList - much like the way the AnyLogic Seize block allows you to specify multiple resource pools to choose from.
Has anyone attempted this before and been successful?
This is possible as follows:
Change the type to "Other" and then 'Tank[]' , i.e. an Array of Tanks
Change the control type to "one-dimensional array"
Example below. Now you have the same UI to pre-define tanks at design time for your agent instance.
In addition to Benjamin's perfect answer, I'd just add the manual workaround, which is not needed here but can be useful when the parameter in question has a more complicated structure than covered by the pre-made controls, say a list of lists, a map, or similar.
In such a case, the Control Type is still Text, and populating it in an instance happens by pointing it to a new object of the parameter's type. E.g. for an ArrayList<Tank> parameter, you might instantiate a new ArrayList object, which you fill with a list of objects like so:
new ArrayList<Tank>(Arrays.asList(tankA, tankB))
In the Java code, whatever is written into that text box will end up on the right side of a parameter assignment statement in the embedded Agent instance's auto-generated parameter setup function. Therefore, multi-statement code won't work in this spot. Instead, if the process of building the parameter value doesn't fit neatly into a single expression, you can hide the code in a function which returns the desired object, and call that from the parameter's text box.
Say i have a public list of integers then of course I will see the list in unity inspector and i can assign multiple values inside it. My question is when the list will actually assign the values to the variables in the game?? Does it assign values in "OnEnable()", "OnAwake()", "OnStart()".
During deserialization
Which occurs before any method of that script's code is called.
If you want to run code at that point in time, you need an ISerializationCallbackReceiver. Note that the intended use of this interface is to serialize/deserialize certain complex Types (such as dictionaries) for use in the Inspector; I have not attempted to use this in a runtime capacity even though the interface does appear to be in UnityEngine not UnityEditor.