Since the documentation and tutorials on collections in Ponylang are lacking, I'm really struggling in using the Array class and working with indices.
I have an overenginered actor-based fizzbuzz where there's an actor in charge of requesting fizzbuzz operations to other actors and collecting the results. Probably the pattern I'm using is not the best but right now I would like to iterate in this way to learn more.
My problem is with the following code:
actor FizzBuzzer
var _results:Array[String]
let _main: Main tag
fun list_to_string(l:List[String]):String=>
l.fold[String]({(a:String,b:String)=>a+"\n"+b},"")
new create(n:String, main:Main tag)=>
let num:USize = try (consume n).usize()? else 0 end
_main = main
_results = recover Array[String] end
try
let result = this.fizzbuzz(num)?
let message:String = list_to_string(result)
main.print(message)
else
main.print("Invalid argument: "+ num.string())
end
fun fizzbuzz(n:USize, acc:List[String]=List[String]()):List[String] ?=>
if n <=0 then error end
let res = List[String]()
for i in Range[USize](1,n+1) do
FizzBuzzerino.process(i,this)
end
res
be collect_result(result:String,num:USize)=>
try
_results.insert(num,result)?
else
_main.print("Error processing element: "+num.string())
end
`
In the function collect_result the insertion always fails. Using update is the same. The result and num I receive from the processing actor are correct but I cannot insert them in the array. Any insertion in the Array in this class fails. Is it a matter of capabilities? Or am I doing something wrong?
Related
I am trying to loop over inputs and process them to produce scores.
Just for the first input, I want to do some processing that takes a while.
The function ends up returning just the values from the 'else' part. The 'if' part is done executing after the function returns the value.
I am new to Scala and understand the behavior but not sure how to fix it.
I've tried inputs.zipWithIndex.map instead of foreach but the result is the same.
def getscores(
inputs: inputs
): Future[Seq[scoreInfo]] = {
var scores: Seq[scoreInfo] = Seq()
inputs.zipWithIndex.foreach {
case (f, i) => {
if (i == 0) {
// long operation that returns Future[Option[scoreInfo]]
getgeoscore(f).foreach(gso => {
gso.foreach(score => {
scores = scores.:+(score)
})
})
} else {
scores = scores.:+(
scoreInfo(
id = "",
score = 5
)
)
}
}
}
Future {
scores
}
}
For what you need, I would drop the mutable variable and replace foreach with map to obtain an immutable list of Futures and recover to handle exceptions, followed by a sequence like below:
def getScores(inputs: Inputs): Future[List[ScoreInfo]] = Future.sequence(
inputs.zipWithIndex.map{ case (input, idx) =>
if (idx == 0)
getGeoScore(input).map(_.getOrElse(defaultScore)).recover{ case e => errorHandling(e) }
else
Future.successful(ScoreInfo("", 5))
})
To capture/print the result, one way is to use onComplete:
getScores(inputs).onComplete(println)
The part your missing is understanding a tricky element of concurrency, and that is that the order of execution when using multiple futures is not guaranteed.
If your block here is long running, it will take a while before appending the score to scores
// long operation that returns Future[Option[scoreInfo]]
getgeoscore(f).foreach(gso => {
gso.foreach(score => {
// stick a println("here") in here to see what happens, for demonstration purposes only
scores = scores.:+(score)
})
})
Since that executes concurrently, your getscores function will also simultaneously continue its work iterating over the rest of inputs in your zipWithindex. This iteration, especially since it's trivial work, likely finishes well before the long-running getgeoscore(f) completes the execution of the Future it scheduled, and the code will exit the function, moving on to whatever code is next after you called getscores
val futureScores: Future[Seq[scoreInfo]] = getScores(inputs)
futureScores.onComplete{
case Success(scoreInfoSeq) => println(s"Here's the scores: ${scoreInfoSeq.mkString(",")}"
}
//a this point the call to getgeoscore(f) could still be running and finish later, but you will never know
doSomeOtherWork()
Now to clean this up, since you can run a zipWithIndex on your inputs parameter, I assume you mean it's something like a inputs:Seq[Input]. If all you want to do is operate on the first input, then use the head function to only retrieve the first option, so getgeoscores(inputs.head) , you don't need the rest of the code you have there.
Also, as a note, if using Scala, get out of the habit of using mutable vars, especially if you're working with concurrency. Scala is built around supporting immutability, so if you find yourself wanting to use a var , try using a val and look up how to work with the Scala's collection library to make it work.
In general, that is when you have several concurrent futures, I would say Leo's answer describes the right way to do it. However, you want only the first element transformed by a long running operation. So you can use the future return by the respective function and append the other elements when the long running call returns by mapping the future result:
def getscores(inputs: Inputs): Future[Seq[ScoreInfo]] =
getgeoscore(inputs.head)
.map { optInfo =>
optInfo ++ inputs.tail.map(_ => scoreInfo(id = "", score = 5))
}
So you neither need zipWithIndex nor do you need an additional future or join the results of several futures with sequence. Mapping the future just gives you a new future with the result transformed by the function passed to .map().
I want to get all the values from a registration page and store all values in an array. How can I do that in protractor?
var arr = new Array(); //declare array
InputName.getAttribute("value")
.then(function(value){
arr[0]=value; // want to store promise value in an array
});
console.log(arr[0]);
If you run your code, it will first log arr[0] and then resolve Promise. Therefore, you may access that array's values in the next Promise. Something like this
var arr = new Array(); // <- this is by the way bad practice, use 'let arr = [];'
InputName.getAttribute("value")
.then(function(value) {
arr[0]=value; // I would use arr.push(value)
});
anotherInput.getAttribute("value")
.then(function(value) {
console.log(arr[0]); // your value should be accessible here
arr.push(value) // push another value
});
But, honestly, I've been working with Protractor fo a while now and I still have difficulties understanding promises... This why I'm using async/await in my tests so if I were to implement something like that I would end up having the following
let arr = [];
let value1 = await InputName.getAttribute("value");
arr.push(value1);
console.log(arr[0]);
Clear, neat code with no hustle. Plus protractor team is actually removing promise_manager, so one day when you update it your code will not work anymore. Then why not switch earlier
i am trying to make a game where players create their own buildings and can then save them for other players to see and play on. However, roblox doesn't let me store all the data needed for the whole creation(there are several properties for each brick)
All i get is this error code:
104: Cannot store Array in DataStore
any help would be greatly appreciated!
I'm not sure if this is the best method, but it's my attempt. Below is an example of a table, you can use tables to store several values. I think you can use HttpService's JSONEncode function to convert tables into strings (which hopefully can be saved more efficiently)
JSONEncode (putting brick's data into a string, which you can save into the DataStore
local HttpService = game:GetService("HttpService")
-- this is an example of what we'll convert into a json string
local exampleBrick = {
["Size"] = Vector3.new(3,3,3),
["Position"] = Vector3.new(0,1.5,0),
["BrickColor"] = BrickColor.new("White")
["Material"] = "Concrete"
}
local brickJSON = HttpService:JSONEncode(exampleBrick)
print(brickJSON)
-- when printed, you'll get something like
-- { "Size": Vector3.new(3,3,3), "Position": Vector3.new(0,1.5,0), "BrickColor": BrickColor.new("White"), "Material": "Concrete"}
-- if you want to refer to this string in a script, surround it with two square brackets ([[) e.g. [[{"Size": Vector3.new(3,3,3)... }]]
JSONDecode (reading the string and converting it back into a brick)
local HttpService = game:GetService("HttpService")
local brickJSON = [[ {"Size": Vector3.new(3,3,3), "Position": Vector3.new(0,1.5,0), "BrickColor": BrickColor.new("White"), "Material": "Concrete"} ]]
function createBrick(tab)
local brick = Instance.new("Part")
brick.Parent = <insert parent here>
brick.Size = tab[1]
brick.Position= tab[2]
brick.BrickColor= tab[3]
brick.Material= tab[4]
end
local brickData = HttpService:JSONDecode(brickJSON)
createBrick(brickData) --this line actually spawns the brick
The function can also be wrapped in a pcall if you want to account for any possible datastore errors.
Encoding a whole model into a string
Say your player's 'building' is a model, you can use the above encode script to convert all parts inside a model into a json string to save.
local HttpService = game:GetService("HttpService")
local StuffWeWantToSave = {}
function getPartData(part)
return( {part.Size,part.Position,part.BrickColor,part.Material} )
end
local model = workspace.Building --change this to what the model is
local modelTable = model:Descendants()
for i,v in pairs(modelTable) do
if v:IsA("Part") or v:IsA("WedgePart") then
table.insert(StuffWeWantToSave, HttpService:JSONEncode(getPartData(modelTable[v])))
end
end
Decoding a string into a whole model
This will probably occur when the server is loading a player's data.
local HttpService = game:GetService("HttpService")
local SavedStuff = game:GetService("DataStoreService"):GetDataStore("blabla") --I don't know how you save your data, so you'll need to adjust this and the rest of the scripts (as long as you've saved the string somewhere in the player's DataStore)
function createBrick(tab)
local brick = Instance.new("Part")
brick.Parent = <insert parent here>
brick.Size = tab[1]
brick.Position= tab[2]
brick.BrickColor= tab[3]
brick.Material= tab[4]
end
local model = Instance.new("Model") --if you already have 'bases' for the players to load their stuff in, remove this instance.new
model.Parent = workspace
for i,v in pairs(SavedStuff) do
if v[1] ~= nil then
CreateBrick(v)
end
end
FilteringEnabled
If your game uses filteringenabled, make sure that only the server handles saving and loading data!! (you probably already knew that) If you want the player to save by clicking a gui button, make the gui button fire a RemoteFunction that sends their base's data to the server to convert it to a string.
BTW I'm not that good at scripting so I've probably made a mistake somehwere.. good luck though
Crabway's answer is correct in that the HttpService's JSONEncode and JSONDecode methods are the way to go about tackling this problem. As it says on the developer reference page for the DataStoreService, Data is ... saved as a string in data stores, regardless of its initial type. (https://developer.roblox.com/articles/Datastore-Errors.) This explains the error you received, as you cannot simply push a table to the data store; instead, you must first encode a table's data into a string using JSONEncode.
While I agree with much of Crabway's answer, I believe the function createBrick would not behave as intended. Consider the following trivial example:
httpService = game:GetService("HttpService")
t = {
hello = 1,
goodbye = 2
}
s = httpService:JSONEncode(t)
print(s)
> {"goodbye":2,"hello":1}
u = httpService:JSONDecode(s)
for k, v in pairs(u) do print(k, v) end
> hello 1
> goodbye 2
As you can see, the table returned by JSONDecode, like the original, uses strings as keys rather than numeric indices. Therefore, createBrick should be written something like this:
function createBrick(t)
local brick = Instance.new("Part")
brick.Size = t.Size
brick.Position = t.Position
brick.BrickColor = t.BrickColor
brick.Material = t.Material
-- FIXME: set any other necessary properties.
-- NOTE: try to set parent last for optimization reasons.
brick.Parent = t.Parent
return brick
end
As for encoding a model, calling GetChildren would produce a table of the model's children, which you could then loop through and encode the properties of everything within. Note that in Crabway's answer, he only accounts for Parts and WedgeParts. You should account for all parts using object:IsA("BasePart") and also check for unions with object:IsA("UnionOperation"). The following is a very basic example in which I do not store the encoded data; rather, I am just trying to show how to check the necessary cases.
function encodeModel(model)
local children = model:GetChildren()
for _, child in ipairs(children) do
if ((child:IsA("BasePart")) or (child:IsA("UnionOperation"))) then
-- FIXME: encode child
else if (child:IsA("Model")) then
-- FIXME: using recursion, loop through the sub-model's children.
end
end
return
end
For userdata, such as Vector3s or BrickColors, you will probably want to convert those to strings when you go to encode them with JSONEncode.
-- Example: part with "Brick red" BrickColor.
color = tostring(part.BrickColor)
print(string.format("%q", color))
> "Bright red"
I suggest what #Crabway said, use HttpService.
local httpService = game:GetService("HttpService")
print(httpService:JSONEncode({a = "b", b = "c"}) -- {"a":"b","b":"c"}
But if you have any UserData values such as Vector3s, CFrames, Color3s, BrickColors and Enum items, then use this library by Defaultio. It's actually pretty nice.
local library = require(workspace:WaitForChild("JSONWithUserdata"))
library:Encode({Vector3.new(0, 0, 0)})
If you want a little documentation, then look at the first comment in the script:
-- Defaultio
--[[
This module adds support for encoding userdata values to JSON strings.
It also supports lists which skip indices, such as {[1] = "a", [2] = "b", [4] = "c"}
Userdata support is implemented by replacing userdata types with a new table, with keys _T and _V:
_T = userdata type enum (index in the supportedUserdataTypes list)
_V = a value or table representing the value
Follow the examples bellow to add suppport for additional userdata types.
~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
Usage example:
local myTable = {CFrame.new(), BrickColor.Random(), 4, "String", Enum.Material.CorrodedMetal}
local jsonModule = require(PATH_TO_MODULE)
local jsonString = jsonModule:Encode(myTable)
local decodedTable = jsonModule:Decode(jsonString)
--]]
Can someone please explain whats the difference between the two in Entity Framework.
Example1:
obj = new TicketsEntities();
var depts = obj.DEPARTMENTs.Select( x => x);
string str = depts.GetType().ToString();
In this case str prints --- System.Data.Entity.Infrastructure.DbQuery`1[LINQu.Models.DEPARTMENT]
Example2:
obj = new TicketsEntities();
var depts = obj.DEPARTMENTs;
string str = depts.GetType().ToString();
In this case str prints --- System.Data.Entity.DbSet`1[LINQu.Models.DEPARTMENT]
In either case when we loop through the depts we get same result , so what is the difference between the two , and which one is preferred ?
The DbSet represents the set of data and can manipulate the data by exposing methods like Add, Update, Remove.
The DbQuery represents a Linq query that is executed on a set of data. It does not have the Add, Update and Remove methods.
In your case I think there is no real difference, but for simplicity sake I would pick your second example since the Select(x=>x) is not neccessary.
I have a service_echo function in a simple chat application which uses SockJS for implementing multi-user private chat. I created an ETS table for the list of online users. By storing SockJS session, I thought to send message to that Connection whenever I receive a message from a different Connection.
Here is my service_echo code.
service_echo(Conn, {recv, Data}, state) ->
Obj = mochijson2:decode(Data),
{struct, JsonData} = Obj,
Name = proplists:get_value(<<"name">>, JsonData),
A = ets:lookup(username,Name),
io:format("~p",[Conn]),
if
length(A) =:= 0 ->
ets:insert(username,{Name,Conn});
true ->
[{AA,BB}] = ets:lookup(username,Name),
BB:send(Data)
end,
io:format("hello");
Even though Conn and BB are same, still Conn:send(data) sends a valid data to the browser while BB:send(Data) does nothing and even does not show an error.
Since I'm a new to Erlang, please excuse me for any unintented mistakes.
First of all, let me advise you on never using length(A) =:= 0 for testing whether the list A is empty or not; if A a long list, counting its elements will cost you a lot, although the result will not actually be used. Use A =:= [] instead, simpler and better.
I don't understand why you're saying that Conn and BB are the same. This does not follow from the code that you have posted here. If Name is not in the table, you insert an entry {Name, Conn}. Otherwise, if Name exists in the table and is related to a single object BB, you assume that this BB is a module and you call the send function defined therein.
It could be that you're reading wrong the semantics of if --- if that's the case, don't let the true guard confuse you, this is how an if-then-else is written in Erlang. Maybe you wanted to have something like:
...
A = ets:lookup(username,Name),
if
A =:= [] ->
ets:insert(username,{Name,Conn})
end,
[{_,BB}] = ets:lookup(username,Name),
BB:send(Data)
...
or even better:
...
A = ets:lookup(T,Name),
if
A =:= [] ->
ets:insert(T,{Name,Conn}),
BB = Conn;
true ->
[{_,BB}] = A
end,
BB:send(Data)
...
On the other hand, it could be that I misunderstood what you're trying to do. If that's the case, please clarify.