I want to check in my app anywhere if the user is an admin or not. For that, I am first fetching the admins list from the server and set a global file that contains ValueNotifier<bool> admin to notify if we have set or change the value of admin after fetching the admin list. But problem is that admin.value setter will also be accessible to all files to set its value, but I want to restrict it such that the value of admin can only be changed in Networks class or Network files or any other specific files, while I want to listen on its changes anywhere possible. Can anyone help me?
You could make your ValueNotifier a private instance so it will only be accessible and editable in its current class then make a public getter for its listenable value which you will be able to call from outside.
Example
class Network{
// private variable only accessible inside the class
final ValueNotifier<bool> _isAdminNotifier = ValueNotifier<bool>(false);
// public getter accessible outside
ValueListenable<bool> get isAdmin => _isAdminNotifier;
}
Try the full example on DartPad.
Ok Got it, I can create a ValueListenable<bool> getter on ValueNotifier<bool> admin.
Related
On main.dart I get response from api username and set `String myUsername = 'stackoverflow';
How on all page use myUsername as global variable?
the answer above is right ,
however if you don't want to make a singleton class,
all you can do is, save it to shared preference, using the
shared_preferences
myPreference.setString("userName", Your user name)
and get it using
myPreference.getString("userName")
You can create a Singleton like this:
class SingletonTest{
String myUsername;
SingletonTest._private();
static SingletonTest _instance = SingletonTest._private();
static SingletonTest get instance => _instance;
}
After that, you can access it from anywhere in your code using:
var singl = SingletonTest.instance;
For more examples refer to:
How to build a Singleton in dart
Or you can use Provider Pattern, more info about it here:
Provider Pattern
In my Ionic 5 project, I have created a custom component and passing the data from a Page.
HomePage HTML:
<app-userItem [inUser]="user (outSync)="syncUser($event)"></app-userItem>
Where user is.
let user = {
Name: 'Test User',
Age: 23
}
Now I want if inside component UserItem I change the value of Age, it should be synced back in the Homepage user variable. It is not happening automatically.
To Achieve this I am using the outSync event emit method for now. My question is as I am using [] to pass value of parameter inUser, shouldn't the user variable be in sync from both sides?
Now I want if inside component UserItem I change the value of Age, it should be synced back in the Homepage user variable. It is not happening automatically.
I think the reason why it's not happening automatically is because Angular compares the object identity to see if something has changed, but in your case, user === user is true even after changing user.age because the instance is still the same.
It doesn't mean the object is not being updated – it's just that Angular doesn't know that because the instance of the object is the same so as far as Angular knows, nothing have been changed.
A better approach would be if the UserItemComponent only presents the data, but doesn't change it directly (which would make it a dumb or presentational component).
For example, if that component could change both the name and the age properties, it'd be better if it just notifies the parent that those properties should be changed, and it's the parent who updates the user.
<app-userItem
[inUser]="user
(updateAge)="updateAge($event)"
(updateName)="updateName($event)"
></app-userItem>
And then the parent component would modify the data, creating a new instance of the object so that the child receives the update:
public updateAge(newAge: number): void {
this.user = {
...this.user,
age: newAge
};
}
I am trying to access a model class in the second page of my app.
In the first which I have named Main Activity I am able to call the class and write an updated value to it. My class is as follows:
class UserDetails{
String userName = "";
String userSurname = "";
}
In MainActivity I am able to call the above and update the userName and userSurname after reading from Firestore and print in the console:
UserDetails details = UserDetails();
details.userName = userName;
details.userSurname = userSurname;
print(details.userName);
print(details.userSurname);
When I move to the second page and try to call the same first two lines shown below I cannot even autocomplete the details.userName.
UserDetails details = UserDetails();
details.userName = userName;
The package is imported on both MainActivity and the second page. any idea why I cannot get UserDetails in the second? I thought maybe it is not re-usable across pages but even if I remove it from MainActivity it still doesnt allow the usage on the second page.
Essentially what I am trying to do is use userName and userSurname as global variables.
if the class is imported in both of your classes.
Run the command flutter clean. That would solve your problem.
I hope this helps.
I'm having difficulties in two areas:
1) When a user successfully logs into their account using phone auth in Firestore, I take them to an "Edit profile" page so they can add their profile information. I get an error saying that I can't add data to a null user class or add data to a class within a class.
I currently have my user class setup something like the following:
class User {
String points;
Name name;
User({this.points, this.name});
}
class Name {
String firstName;
String lastName;
Name({this.firstName, this.lastName})
}
As you can see, I have a class within a class and when I try to add a value, it says I can't. I've tried doing it like
_bloc.user.name.firstName = value
And I've tried like
Name newName = Name();
newName.first = value.
The second one seems to work but it doesn't seem right. I'm hoping you could help me understand how to properly approach adding data for new users when I have a class within a class.
The second issue is understanding how to properly use the Places API. I'm currently learning from the below repo, but it's outdated and there's a couple lines I can't seem to figure out how to change. I also can't seem to find an updated tutorial since the October app crashing update.
https://github.com/alfianlosari/flutter_placez
Thanks in advance for your help!
how to save class extend in grails?
example i have class user and administrator
class User {
String name
String password
}
class Administrator extends User {
String authoritySelected
}
example in class User i have save "user1",
and then i want to change user1 from class user to class administrator and update authoritySelected
def update(){
def user1 = User.get("user1")
user1.authoritySelected
user1.save(flush:true)
}
and get error :
No such property: authoritySelected for class:User
so, how to save authoritySelected in class User and change that to class Administrator? thanks.
Speaking about the syntax, the code you wrote has no sense. Speaking about design, neither.
May I suggest you to study a bit a OOP before attempting doing this kind of stuff? :)
But let's face the problem you submitted.
First suggestion: don't implement the security system for your application, there's a lot of stuff that can do it for you. One above all: Spring Security plugin.
Second: the code you wrote doesn't work because extending a class is a way to make another class 'son' of the parent. In you example, Administrator is a son of User.
def update(){
def user1 = User.get("user1") // I don't get how this should work, but I'll leave it like this in this example
user1.authoritySelected // you're trying to GET the value a property that doesn't exist in the User class, you should SET something here
user1.save(flush:true)
}
If you want your User to change role, the easiest think is to think at the role not as another class, instead it should be an attribute of the User, so you can change it. Once the instance of a class is created, you can't change it (probably this is not totally true, but you shouldn't).
OK, some code:
class User {
String name
String password
String authority // a property of the class you can change
}
def update(){
def user1 = User.get("user1")
user1.authority = 'Administrator' // change the property on the instance you retrieved
user1.save() // save the instance itself
}
This is still not a good design solution to me, I'm just trying to make you able to see what you're doing wrong.
When you say "and then i want to change user1 from class user to class administrator", what exactly are you trying to do?
You are trying to access a property of an object that doesn't exist in that object. Downcasting simply doesn't work like that. You should instantiate an object of type Administrator in order to save one of its properties after.
if you want to create a USER you have to create an USER's instance, for example:
User u = new User(name: "xpto", password: "xptopass").save(flush:true)
An Administrator is a USER too, but with one more data, the authoritySelected, so if the Administrator extends User, he have the same data like a User too.
Administrator a = new Administrator(name: "xpto", password: "xptopPass", authoritySelected: "ADMIN").save(flush:true)
Attention, Object.get(X) methods needs an ID (Long), "X" would be a Long value, not a String.
http://grails.org/doc/2.3.x/ref/Domain%20Classes/get.html