When I try to create a constructor in dart like Student(this._name) it doesn't work with private variables.
I have already tried using setters but it doesn't work either.
class Student{
var _id;
var _name;
Student(this.id, this.name);
void set id(int id) => _id = id;
void set name(String name) => _name = name;
}
This is not supported because it would expose private implementation to the outside.
If you'd rename var _id; to var _userId; you would break code that uses your class just by renaming a private field.
See instead the comment below my answer.
class Student{
var _id;
var _name;
Student({this._id, this._name}); // error
void set id(int id) => _id = id;
void set name(String name) => _name = name;
}
The alternative
class Student{
var _id;
var _name;
Student({int id, String name}) : _id = id, _name = name;
void set id(int id) => _id = id;
void set name(String name) => _name = name;
}
You can use this notation
class Student {
String _id;
String _name;
Student({required String id, required String name})
: _id = id,
_name = name;
}
Some of you maybe struggle if the class was inheritance, you just need add coma (,) after initialize your private.
Example
class Animal {
String _name;
int _age;
}
class Dog extends Animal {
String _race;
Dog(String name, int age, {String? race}) : _race = race ?? "Wild", super(name, age);
}
Hope this code can help you.
This notation is not valid because the variable is not private and its elements are just as accessible again.
DartLang says: AVOID wrapping fields in getters and setters just to be "safe".
Related
class Persons {
final String name;
final String age;
Persons(
this.name,
this.age,
);
void printName() {
print(name);
}
}
class Players extends Persons {}
enter image description here
Edit the class Players
class Players extends Persons {
Players(name, age): super(name, age);
}
How do I create a null safe constructor with Syntactic sugar that would set a default value if the provided value is null?
class Person {
Person({
required this.name, //Idealy, adding (?? "friend") instead of "required" should've worked but doesn't.
required this.age,
});
String name;
int age;
greet() {
print("Hello $name");
}
}
So, I actually want something like this,
class Person {
Person({
this.name ?? "friend",
this.age ?? 0,
});
String name;
int age;
greet() {
print("Hello $name");
}
}
But, as you know this is not valid in dart. So, how actually, should I achieve this?
class Person {
Person({
String? name,
int? age,
}) : this.name = name ?? "friend",
this.age = age ?? 0;
String name;
int age;
void greet() {
print("Hello $name");
}
}
Constructor Optional Params
for selecting my proposal
select this as an answer (converted from comment with permission)
You can also use default values for your optional parameters:
class Person {
Person({
this.name = "friend",
this.age = 0,
});
String name;
int age;
greet() {
print("Hello $name");
}
}
The parameter is not required, and if you don't pass it, it gets the default value. If you do pass an argument, it must be non-null.
I am trying to bind a textfield to an object. I've done some research and I have found this answer.
public class Person {
String name;
String surname;
Address address;
// assume getters and setters
}
public class Address {
String street;
// assume getter and setters
}
Then, you could bind the street address like this:
Binder<Person> binder = new Binder<>();
TextField streetAddressField = new TextField();
// bind using lambda expressions
binder.bind(streetAddressField,
person -> person.getAddress().getStreet(),
(person, street) -> person.getAddress().setStreet(street));
What value do I instantiate street as (in the last line of code)?
The above was the example I found. My code is as follows - I have a contact class:
#Entity
public class Contact {
#Id
#GeneratedValue
private Long id;
private String firstName;
private String lastName;
private String phoneNumber;
#ManyToOne (cascade = {CascadeType.ALL})
#JoinColumn(name="phoneType_typeId")
private PhoneType phoneType;
public Contact(){
}
public Contact(String firstName, String lastName, String phoneNumber, PhoneType type) {
this.firstName = firstName;
this.lastName = lastName;
this.phoneNumber = phoneNumber;
this.phoneType = type;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getFirstName() {
return firstName;
}
public void setFirstName(String firstName) {
this.firstName = firstName;
}
public String getLastName() {
return lastName;
}
public void setLastName(String lastName) {
this.lastName = lastName;
}
public String getPhoneNumber() {
return phoneNumber;
}
public void setPhoneNumber(String phoneNumber) {
this.phoneNumber = phoneNumber;
}
public PhoneType getPhoneType() {
return phoneType;
}
public void setPhoneType(PhoneType phoneType) {
this.phoneType = phoneType;
}
#Override
public String toString() {
return String.format("Contact[firstName='%s', lastName='%s', phoneNumber='%s', phoneType = '%s']",
firstName, lastName, phoneNumber, phoneType);
}
}
Then I have a phoneType class:
#Entity
#Table(name="phoneType")
public class PhoneType {
#Id
#GeneratedValue
#Column(name = "typeId")
private Long id;
private String type;
public PhoneType(String type){
this.type = type;
}
public PhoneType(){}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getType() {
return type;
}
public void setType(String type) {
this.type = type;
}
#Override
public String toString() {
return type;
}
}
Then in a Contact Editor I am trying to bind the phoneType to a textfield:
#SpringComponent
#UIScope
public class ContactEditor extends VerticalLayout {
private final ContactRepository repository;
private Contact contact;
TextField firstName = new TextField("First name");
TextField lastName = new TextField("Last name");
TextField phoneNumber = new TextField("Phone number");
TextField phoneType = new TextField( "Phone type");
Button save = new Button("Save", VaadinIcons.CHECK);
Button cancel = new Button("Cancel");
Button delete = new Button("Delete", VaadinIcons.TRASH);
CssLayout actions = new CssLayout(save, cancel, delete);
Binder<Contact> binder = new Binder<>(Contact.class);
#Autowired
public ContactEditor(ContactRepository repository, Contact contact) {
this.repository = repository;
this.contact = contact;
String type = contact.getPhoneType().getType();
addComponents(firstName, lastName, phoneNumber, phoneType, actions);
// bind using naming convention
**binder.bind(phoneType, contact.getPhoneType().getType(), contact.getPhoneType().setType(type));**
binder.bindInstanceFields(this);
// Configure and style components
setSpacing(true);
actions.setStyleName(ValoTheme.LAYOUT_COMPONENT_GROUP);
save.setStyleName(ValoTheme.BUTTON_PRIMARY);
save.setClickShortcut(ShortcutAction.KeyCode.ENTER);
// wire action buttons to save, delete and reset
save.addClickListener(e -> repository.save(contact));
delete.addClickListener(e -> repository.delete(contact));
cancel.addClickListener(e -> editContact(contact));
setVisible(false);
}
public interface ChangeHandler {
void onChange();
}
public final void editContact(Contact c) {
if (c == null) {
setVisible(false);
return;
}
final boolean persisted = c.getId() != null;
if (persisted) {
// Find fresh entity for editing
contact = repository.findById(c.getId()).get();
}
else {
contact = c;
}
cancel.setVisible(persisted);
// Bind customer properties to similarly named fields
// Could also use annotation or "manual binding" or programmatically
// moving values from fields to entities before saving
binder.setBean(contact);
setVisible(true);
// A hack to ensure the whole form is visible
save.focus();
// Select all text in firstName field automatically
firstName.selectAll();
}
public void setChangeHandler(ChangeHandler h) {
// ChangeHandler is notified when either save or delete
// is clicked
save.addClickListener(e -> h.onChange());
delete.addClickListener(e -> h.onChange());
}
}
The line enclosed in ** in Contact Editor (i.e. binder.bind(phoneType, contact.getPhoneType().getType(), contact.getPhoneType().setType(type))) is giving me an error - "no instance of type variable FIELDVALUE exist so that string conforms to ValueProvider .
The line
binder.bind(phoneType, contact.getPhoneType().getType(), contact.getPhoneType().setType(type));
does not compile because the method arguments do not match to any of the bind methods, and there is an illegal Java expression in the 3rd argument. According to your question, you have simply forgotten to use lambdas. Try:
binder.bind(phoneType, c -> c.getPhoneType().getType(), (c, t) -> c.getPhoneType().setType(t));
Have a look at the method signature:
public <FIELDVALUE> Binder.Binding<BEAN,FIELDVALUE> bind(HasValue<FIELDVALUE> field,
ValueProvider<BEAN,FIELDVALUE> getter,
Setter<BEAN,FIELDVALUE> setter)
It expects ValueProvider and Setter as 2nd and 3rd argument. These interfaces have only one method to be implemented, therefore you can use lambdas to pass them to bind.
I don't know if this is what you'r asking, but what I see as missing is that you haven't binded your binder to any bean.
You have created the binder, and you've told your textfield which property is binded to, but now you need to tell the binder which is his bean.
Something like:
Person yourPerson = new Person(); //or get person from database somehow
yourPerson.setAddress(new Address());
yourPerson.getAddress().setStreet("Road cool code, 404");
binder.setBean(yourPerson);
This should do the trick... if not, please explain better what you need. ;)
Is there a way to map fields from classes to one using Orika.
Can't find the solution in the orika documentation.
In the example the fields test & name from class ObjectOne should be mapped to the corresponding fields ObjectNew.
public class ObjectOne {
private String test;
private String name;
private String id;
public ObjectOne(String id,String test, String name){
this.id=id;
this.test=test;
this.name=name;
}
}
The same with field sheet from ObjectTwo
public class ObjectTwo {
private String sheet;
private String id;
public ObjectTwo(String id,String sheet){
this.id=id;
this.sheet=sheet;
}
}
Code for ObjectNew
public class ObjectNew {
private String id;
private String test;
private String name;
private String sheet;
public ObjectNew(String id,String test,String name,String sheet){
this.id=id;
this.test=test;
this.name = name;
this.sheet = sheet;
}
}
Fields from both classes ObjectOne & ObjectTwo should initiate new object ObjectNew when id's of classes ObjectOne and ObjectTwo are the same.
Any ideas how to handle this?
Kind Regards
I would suggest to wrap the source objects into one source wrapper object and map this new wrapper object with your new object:
public class objectWrapper{
private objectOne objectOne;
private objectTwo objectTwo;
}
I am new to Neo4J. I have built a project that uses spring-data-neo4j (4.0.0.BUILD-SNAPSHOT - version), spring-boot (1.2.3.RELEASE - version) and succeeded to create node entities, add properties to node entities and add relationships. It works fine. Now I want to create properties for the relationships. I have used sdn4 university as a reference, here is the link https://github.com/neo4j-examples/sdn4-university .
I want to create a property called "challengedBy" for relationship PLAY_MATCH (Start node is Match and end node is Player). You can have a look on below class.
#RelationshipEntity(type = "PLAY_MATCH")
public class PlayMatch extends Entity {
//Entity is a class with the id property for the node / relationship
#Property
private String challengedBy;
#StartNode
private Match match;
#EndNode
private Player player1;
}
I have created a controller in the project /api/playmatch to create only the relationship between match and a player. So when I pass the values for an existing match node and a player node, the relationship is not created at all.
Any help will be appreciated..
PlayMatch code is
#RelationshipEntity(type = "PLAY_MATCH")
public class PlayMatch extends Entity{
#Property
private String challengedBy;
#StartNode
private Match match;
#EndNode
private Player player1;
public PlayMatch() {
}
public PlayMatch(String challengedBy, Match match,
Player player1) {
super();
this.challengedBy = challengedBy;
this.match = match;
this.player1 = player1;
}
// after this i have getters & setters and toString method for above fields.
}
Match code is
#NodeEntity(label = "Match")
public class Match extends Entity {
private String createdBy;
private Long createdTime;
private String status;
private int noOfGames;
private int noOfPoints;
private String type;
private Long date;
#Relationship(type="PLAY_MATCH",direction= Relationship.UNDIRECTED)
private PlayMatch playMatch;
public Match() {
}
public Match(String createdBy, Long createdTime, String status,
int noOfGames, int noOfPoints, String type, Long date) {
super();
this.createdBy = createdBy;
this.createdTime = createdTime;
this.status = status;
this.noOfGames = noOfGames;
this.noOfPoints = noOfPoints;
this.type = type;
this.date = date;
}
public PlayMatch getPlayMatch() {
return playMatch;
}
public void setPlayMatch(PlayMatch playMatch) {
this.playMatch = playMatch;
}
// after this i have getters & setters and toString method for above fields.
}
Player code is
#NodeEntity(label = "Player")
public class Player extends Entity {
private String address;
private String preferredSport;
private float height;
private float weight;
private String phone;
private String photo;
#Relationship(type="PLAY_MATCH")
private PlayMatch playMatch;
public PlayMatch getPlayMatch() {
return playMatch;
}
public void setPlayMatch(PlayMatch playMatch) {
this.playMatch = playMatch;
}
public Player() {
}
public Player(String address, String preferredSport, float height,
float weight, String phone, String photo) {
super();
this.address = address;
this.preferredSport = preferredSport;
this.height = height;
this.weight = weight;
this.phone = phone;
this.photo = photo;
}
// after this i have getters & setters and toString method for above fields.
}
I think you have playmatch relationship within the player end node as well. If you comment the following code in the player node. It should work. I have also attached a json sample to pass from the UI in the match URL (/api/match) instead of (/api/playmatch)
#Relationship(type="PLAY_MATCH")
private PlayMatch playMatch;
public PlayMatch getPlayMatch() {
return playMatch;
}
public void setPlayMatch(PlayMatch playMatch) {
this.playMatch = playMatch;
}
Sample JSON
{
"type": "typename",
"status": "statusname",
"createdTime": 1435928223021,
"noOfGames": 5,
"noOfPoints": 19,
"playMatch": {"challengedBy" : "John", "player1" : {"id":732}, "match":{"type": "typename",
"status": "statusname",
"createdTime": 1435928223021,
"noOfGames": 5,
"noOfPoints": 19}}
}
this should create a new match and a new relationship with property challengedBy to an existing player node with id 732.
check it out and let me know if this works.