I am using a Gee.ArrayList with an own class for content. I want to use the "contains" method of the ArrayList, but I really don't know how to set up an equals-method in my class, so ArrayList uses it to find out if the object is in the ArrayList or not.
Example:
class Test : GLib.Object {
public int number;
public Test(int n) {
number = n;
}
public bool equals (Test other) {
if (number == other.number) return true;
return false;
}
}
Then, in another file:
var t = new Gee.ArrayList<Test>();
var n1 = new Test(3);
var n2 = new Test(3);
t.add(n1);
t.contains(n2); // returns false, but I want it to return true
Does anybody know that?
When you create the ArrayList, the constructor takes your equality comparator. You can do:
var t = new Gee.ArrayList<Test>(Test.equals);
and the contains should work as you desire.
Related
Consider this class that is used as a data model in a Model-View-Controller scenario (I'm using TypeScript 3.5):
export class ViewSource {
private viewName : string;
private viewStruct : IViewStruct;
private rows : any[];
private rowIndex : number|null;
constructor(viewName : string) {
// Same as this.setViewName(viewName);
this.viewName = viewName;
this.viewStruct = api.meta.get_view_struct(viewName);
if (!this.viewStruct) {
throw new Error("Clould not load structure for view, name=" + (viewName));
}
this.rows = [];
this.rowIndex = null;
}
public setViewName = (viewName: string) => {
this.viewName = viewName;
this.viewStruct = api.meta.get_view_struct(viewName);
if (!this.viewStruct) {
throw new Error("Clould not load structure for view, name=" + (viewName));
}
this.rows = [];
this.rowIndex = null;
}
public getViewStruct = ():IViewStruct => { return this.viewStruct; }
public getCellValue = (rowIndex: number, columnName: string) : any => {
const row = this.rows[rowIndex] as any;
return row[columnName];
}
}
This is not a complete class, I only included a few methods to demonstrate the problem. ViewSource is a mutable object. It can be referenced from multiple parts of the application. (Please note that being a mutable object is a fact. This question is not about choosing a different data model that uses immutable objects.)
Whenever I want to change the state of a ViewSource object, I call its setViewName method. It does work, but it is also very clumsy. Every line of code in the constructor is repeated in the setViewName method.
Of course, it is not possible to use this constructor:
constructor(viewName : string) {
this.setViewName(viewName);
}
because that results in TS2564 error:
Property 'viewStruct' has no initializer and is not definitely assigned in the constructor.ts(2564)
I do not want to ignore TS2564 errors in general. But I also do not want to repeat all attribute initializations. I have some other classes with even more properties (>10), and the corresponding code duplication looks ugly, and it is error prone. (I might forget that some things have to bee modified in two methods...)
So how can I avoid duplicating many lines of code?
I think the best method to avoid code duplication in this case would be to create a function that contains the initialization code, but instead of setting the value, it retunrs the value that need to be set.
Something like the following:
export class ViewSource {
private viewName : string;
private viewStruct : IViewStruct;
private rows : any[];
private rowIndex : number|null;
constructor(viewName : string) {
const {newViewName, newViewStruct, newRows, newRowIndex} = this.getNewValues(viewName);
this.viewName = newViewName;
this.newViewStruct = newViewStruct;
// Rest of initialization goes here
}
public setViewName = (viewName: string) => {
const {newViewName, newViewStruct, newRows, newRowIndex} = this.getNewValues(viewName);
// Rest of initialization goes here
}
privat getNewValues = (viewName) => {
const newViewName = viewName;
const newViewStruct = api.meta.get_view_struct(viewName);
if (!newViewStruct) {
throw new Error("Clould not load structure for view, name=" + (viewName));
}
const newRows = [];
const newRowIndex = null;
return {newViewName, newViewStruct, newRows, newRowIndex};
}
}
This way the only thing you duplicate is setting the values, not calculating them, and if the values calculations will get more complicated you can simply expand the returned value.
A less complex approach than the accepted answer is to use the //#ts-ignore[1] comment above each member that is initialized elsewhere.
Consider this contrived example
class Foo {
// #ts-ignore TS2564 - initialized in the init method
a: number;
// #ts-ignore TS2564 - initialized in the init method
b: string;
// #ts-ignore TS2564 - initialized in the init method
c: number;
constructor(a: number, b: string) {
if(a === 0) {
this.init(a,b,100);
} else {
this.init(a,b,4912);
}
}
private init(a: number, b: string, c: number): void {
this.a = a;
this.b = b;
this.c = c;
}
}
Since TypeScript 3.9 there exists the //#ts-expect-error[2] comment, but I think #ts-ignore is suitable.
[1] Suppress errors in .ts files
[2] TS expect errors comment
Since TypeScript 2.7 you can use the definite assignment assertion modifier which means adding an exclamation mark between the variable name and the colon:
private viewName!: string
This has the same effect as adding a // #ts-ignore TS2564 comment above it as #RamblinRose suggested.
Using Dart here.
As the above title suggests, I have a class (shown below) that has three bool instance variables. What I want to do is create a function that inspects the identifier names of these instance variables and prints each of them out in a string. The .declarations getter that comes with the ClassMirror class ALMOST does this, except it also gives me the name of the Constructor and any other methods I have in the class. This is no good. So really what I want is a way to filter by type (i.e., only give me the boolean identifiers as strings.) Any way to do this?
class BooleanHolder {
bool isMarried = false;
bool isBoard2 = false;
bool isBoard3 = false;
List<bool> boolCollection;
BooleanHolder() {
}
void boolsToStrings() {
ClassMirror cm = reflectClass(BooleanHolder);
Map<Symbol, DeclarationMirror> map = cm.declarations;
for (DeclarationMirror dm in map.values) {
print(MirrorSystem.getName(dm.simpleName));
}
}
}
OUTPUT IS:
isMarried
isBoard2
isBoard3
boolsToStrings
BooleanHolder
Sample code.
import "dart:mirrors";
void main() {
var type = reflectType(Foo);
var found = filter(type, [reflectType(bool), reflectType(int)]);
for(var element in found) {
var name = MirrorSystem.getName(element.simpleName);
print(name);
}
}
List<VariableMirror> filter(TypeMirror owner, List<TypeMirror> types) {
var result = new List<VariableMirror>();
if (owner is ClassMirror) {
for (var declaration in owner.declarations.values) {
if (declaration is VariableMirror) {
var declaredType = declaration.type;
for (var type in types) {
if (declaredType.isSubtypeOf(type)) {
result.add(declaration);
}
}
}
}
}
return result;
}
class Foo {
bool bool1 = true;
bool bool2;
int int1;
int int2;
String string1;
String string2;
}
Output:
bool1
bool2
int1
int2
Problem:
Is it possible to cast dynamically to a type?
For example, could this be possible, using mirrors:
var reflectee = im.getField(simpleName).reflectee;
var converted = testVal as reflectee.runtimeType;
Context:
I want to make a Mixin class which defines a validate method:
abstract class Validatable {
bool validate(Map document) {
}
}
It will iterate over the variables defined for the class where it is mixed in, and checks if the variable in the document are of the same type.
Now, it is working with getting the runtimeType of the respective variables, but it is very restrictive as it does not cast. For example:
var a = 1.1;
var b = 1;
print(a.runtimeType == b.runtimeType); // false
It would be better to better to check with as, but I cant see how to get this to work. Becase:
a = b;
print(a.runtimeType); // int
and not double, as one might expect.
Is it possible?
You could use
import 'dart:mirrors';
class A {
}
class B extends A {
}
class C extends A {
}
void main(args) {
var a = 1.1;
var b = 1;
var x = reflect(b);
print(x.type.isSubtypeOf(reflectType(num)));
print(x.type.isAssignableTo(reflectType(num)));
print(x.type.isAssignableTo(reflectType(double)));
var myb = new B();
print(reflect(myb).type.isSubtypeOf(reflectType(A)));
print(reflect(myb).type.isAssignableTo(reflectType(A)));
print(reflect(myb).type.isAssignableTo(reflectType(C)));
}
Below is the code from the DotNetNuke Sample module that gets a collection of items from the database that belong to a particular module. What I want is add a second parameter for it filter by. I'm guessing this has something to do with modifying the scope item.cs class but am not sure how exactly.
public IEnumerable<Item> GetItems(int moduleId)
{
IEnumerable<Item> t;
using (IDataContext ctx = DataContext.Instance())
{
var rep = ctx.GetRepository<Item>();
t = rep.Get(moduleId);
}
return t;
}
Any ideas?
Another way to do it in DAL2 is using the .Find() method. This is good if you want to query on an indexed field in your table and you don't care about caching scope:
public IEnumerable<Item> GetItemByName(int moduleId, string itemname)
{
IEnumerable<Item> t;
using (IDataContext ctx = DataContext.Instance())
{
var rep = ctx.GetRepository<Item>();
t = rep.Find("WHERE ModuleId = #0 AND ItemName LIKE #1", moduleId, itemname);
}
return t;
}
Here's some sample code from my SignalRChat module that uses DAL2 (http://signalrchat.codeplex.com/SourceControl/changeset/view/71473#1272188)
public IEnumerable<Message> GetRecentMessages(int moduleId, int hoursBackInTime, int maxRecords)
{
var messages = (from a in this.GetMessages(moduleId) where a.MessageDate.Subtract(DateTime.UtcNow).TotalHours <= hoursBackInTime select a).Take(maxRecords).Reverse();
return messages.Any() ? messages : null;
}
That is one approach, you can also use a SQL statement within the controller as well (http://signalrchat.codeplex.com/SourceControl/changeset/view/71473#1272186)
public ConnectionRecord GetConnectionRecordByConnectionId(string connectionId)
{
ConnectionRecord t;
using (IDataContext ctx = DataContext.Instance())
{
var connections = ctx.ExecuteQuery<ConnectionRecord>(CommandType.Text,
string.Format(
"select top 1 * from {0}{1}SignalRChat_ConnectionRecords where ConnectionId = '{2}'",
_databaseOwner,
_objectQualifier,
connectionId)).ToList();
if (connections.Any())
{
t = connections[0];
}
else
return null;
}
return t;
}
I need to perform some initialization when new instances of my domain class are created.
class ActivationToken {
String foo
String bar
}
When I do this I want bar to be initialized by code inside ActivationToken:
def tok = new ActivationToken(foo:'a')
I cannot see how to 'override' the 'constructor' to make this happen. I know in this case I could just add a normal constructor but this is just a simple example.
The map constructor is coming from Groovy - not Grails in this case. I did some experimentation, and this is what I came up with:
class Foo {
String name = "bob"
int num = 0
public Foo() {
this([:])
}
public Foo(Map map) {
map?.each { k, v -> this[k] = v }
name = name.toUpperCase()
}
public String toString() {
"$name=$num"
}
}
assert 'BOB=0' == new Foo().toString()
assert 'JOE=32' == new Foo(name:"joe", num: 32).toString()
Basically, it appears that you'll have to manually override the constructors if you need to process the property after construction.
Alternately, you can override individual setters, which is cleaner and safer in general:
class Foo {
String name = "bob"
int num = 0
public void setName(n) {
name = n.toUpperCase()
}
public String toString() {
"$name=$num"
}
}
assert 'bob=0' == new Foo().toString()
assert 'JOE=32' == new Foo(name:"joe", num: 32).toString()
Note that the default value isn't processed, but that should be OK in most instances.
The solution above is also good for cases where initializing an object from parameters in a web request, for example, where you wish to ignore extraneous values, catching Missing property exceptions.
public Foo(Map map) {
try {
map?.each { k, v -> this[k] = v }
}
catch(Exception e){
}
}