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  • Rails: update_attribute vs update_attributes

    - by Sam
    Object.update_attribute(:only_one_field, "Some Value") Object.update_attributes(:field1 => "value", :field2 => "value2", :field3 => "value3") Both of these will update an object without having to explicitly tell AR to update. Rails API says: for update_attribute Updates a single attribute and saves the record without going through the normal validation procedure. This is especially useful for boolean flags on existing records. The regular update_attribute method in Base is replaced with this when the validations module is mixed in, which it is by default. for update_attributes Updates all the attributes from the passed-in Hash and saves the record. If the object is invalid, the saving will fail and false will be returned. So if I don't want to have the object validated I should use update_attribute. What if I have this update on a before_save, will it stackoverflow? My question is does update_attribute also bypass the before save or just the validation. Also, what is the correct syntax to pass a hash to update_attributes... check out my example at the top.

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  • How to pickle and unpickle objects with self-references and from a class with slots?

    - by EOL
    Is it possible to pickle an object from a class with slots, when this object references itself through one of its attributes? Here is a simple example: import weakref import pickle class my_class(object): __slots__ = ('an_int', 'ref_to_self', '__weakref__') def __init__(self): self.an_int = 42 self.ref_to_self = weakref.WeakKeyDictionary({self: 1}) # __getstate__ and __setstate__ not defined: how should this be done? if __name__ == '__main__': obj = my_class() # How to make the following work? obj_pickled = pickle.dumps(obj) obj_unpickled = pickle.loads(obj_pickled) # Self-references should be kept: print "OK?", obj_unpickled == obj_unpickled.ref_to_self.keys()[0]

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  • Confused by "let" in Clojure

    - by Tom Dalling
    I just started playing with Clojure, and I wrote a small script to help me understand some of the functions. It begins like this: (def *exprs-to-test* [ "(filter #(< % 3) '(1 2 3 4 3 2 1))" "(remove #(< % 3) '(1 2 3 4 3 2 1))" "(distinct '(1 2 3 4 3 2 1))" ]) Then it goes through *exprs-to-test*, evaluates them all, and prints the output like this: (doseq [exstr *exprs-to-test*] (do (println "===" (first (read-string exstr)) "=========================") (println "Code: " exstr) (println "Eval: " (eval (read-string exstr))) ) ) The above code is all working fine. However, (read-string exstr) is repeated so I tried to use let to eliminate the repetition like so: (doseq [exstr *exprs-to-test*] (let [ex (read-string exstr)] ( (do (println "===" (first ex) "=========================") (println "Code: " exstr) (println "Eval: " (eval ex)) ) )) ) But this works once for the first item in *exprs-to-test*, then crashes with a NullPointerException. Why is the addition of let causing the crash?

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  • Compress small strings, With what to create external dictionary?

    - by Chris
    I want to compress much small strings (about 75-100 length c# string). At the time the dictionary is created I already know all short strings (nearly a trillion). There will no additional short strings in future. I need to extra exactly one string without decompress other strings. Now I am looking for a library or the best way to do the following: Create a dictionary using all strings I have Using this dictionary to compress each string a way to compress one string using the dictionary from 1. I found a good related question, but this is not c# specific. Maybe there is something for c# I do not know, or a fancy library or someone has already done that. That is the reason I ask this question.

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  • C++, is it possible to call a constructor directly, without new?

    - by osgx
    Hello Can I call constructor explicitly, without using new, if I already have a memory for object? // class Object1{char *str;public:Object1(char*str):str(str){puts("ctor");puts(str);};~Object1(){puts("dtor");puts(str);}}; Object1 ooo[2] = {Object1("I'm the first object"), Object1("I'm the 2nd")}; do_smth_useful(ooo); ooo[0].~Object1(); // call destructor ooo[0].Object1("I'm the 3rd object in place of first"); // ???? - reuse memory

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  • STL map - insert or update

    - by CodeJunkie
    I have a map of objects and I want to update the object mapped to a key, or create a new object and insert into the map. The update is done by a different function that takes a pointer to the object (void update(MyClass *obj)) What is the best way to "insert or update" an element in a map?

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  • [Ruby on Rails] complex model relationship

    - by siulamvictor
    I am not sure am I doing these correct. I have 3 models, Account, User, and Event. Account contains a group of Users. Each User have its own username and password for login, but they can access the same Account data under the same Account. Events is create by a User, which other Users in the same Account can also read or edit it. I created the following migrations and models. User migration class CreateUsers < ActiveRecord::Migration def self.up create_table :users do |t| t.integer :account_id t.string :username t.string :password t.timestamps end end def self.down drop_table :users end end Account migration class CreateAccounts < ActiveRecord::Migration def self.up create_table :accounts do |t| t.string :name t.timestamps end end def self.down drop_table :accounts end end Event migration class CreateEvents < ActiveRecord::Migration def self.up create_table :events do |t| t.integer :account_id t.integer :user_id t.string :name t.string :location t.timestamps end end def self.down drop_table :events end end Account model class Account < ActiveRecord::Base has_many :users has_many :events end User model class User < ActiveRecord::Base belongs_to :account end Event model class Event < ActiveRecord::Base belongs_to :account belongs_to :user end so.... Is this setting correct? Every time when a user create a new account, the system will as for the user information, i.e. username and password. How can I add them into correct tables? How can I add a new event? I am sorry for such a long question. I am not very understand the rails way in handling such data structure. Thank you guys for answering me. :)

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  • List.AddRange inline declaration

    - by AJ
    Hello, This may seem an easy question, but not to me, also a search has led to nothing. Up until now the only .net programming I have done is with Delphi Prism. With Prism I can do things like: var l := new List<String>(['A','B','C']); or var l := new List<String>; l.AddRange(['A','B','C']; but can I do a similar thing in C#, or do I have to do it like: var a = new String[] {"A","B","C"}; var l = new List<String>(a); Thanks, AJ

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  • What is a better, cleaner way of using List<T>

    - by Tim Meers
    I'm looking to implement a few nicer ways to use List in a couple of apps I'm working on. My current implementation looks like this. MyPage.aspx.cs protected void Page_Load(object sender, EventArgs e) { BLL.PostCollection oPost = new BLL.PostCollection(); oPost.OpenRecent(); rptPosts.DataSource = oArt; rptPosts.DataBind(); } BLL Class(s) public class Post { public int PostId { get; set; } public string PostTitle { get; set; } public string PostContent { get; set; } public string PostCreatedDate { get; set; } public void OpenRecentInitFromRow(DataRow row) { this.PostId = (int) row["id"]; this.PostTitle = (string) row["title"]; this.PostContent = (string) row["content"]; this.PostCreatedDate = (DateTime) row["createddate"]; } } public class PostCollection : List<Post> { public void OpenRecent() { DataSet ds = DbProvider.Instance().Post_ListRecent(); foreach (DataRow row in ds.Tables[0].Rows) { Post oPost = new Post(); oPost.OpenRecentInitFromRow(row); Add(oPost); } } } Now while this is working all well and good, I'm just wondering if there is any way to improve it, and just make it cleaner that having to use the two different classes do to something I think can happen in just one class or using an interface.

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  • How to replace {tag_INDEX} with array[INDEX] element

    - by ekapek
    Hi, I have string like this; "String {tag_0} text {tag_2} and {tag_1}" Now i need to replace all {tag_INDEX} with elements from array $myArray = array('a','b','c'); so after replacement it should looks like: "String a text c and b" What is the best way to do this? I'm trying with preg_replace and preg_replace_callback but without any good results

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  • C# BestPractice: Private var and Public Getter/Setter or Public Var

    - by Desiny
    What are the advantages and differences between the below two coding styles... public void HelloWorld () { private string _hello; public string Hello { get { return _hello; } set { _hello = value; } } } or public void HelloWorld () { public string Hello { get; set; } } My preference is for short simple code, but interested to hear opinions as I see many developers who insist on the long route.

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  • DisplayObject not being displayed in AS3

    - by MarkSteve
    I have this class: public class IskwabolText extends Sprite { private var _tf:TextField; private var _tfmt:TextFormat; private var _size:Number; private var _text:String; public function IskwabolText(params:Object) { var defaultParams:Object = { color: 0x000000, background: false, backgroundColor: 0xFFFFFF, width: 0, height: 0, multiline: false, wordWrap: false }; // textfield _tf = new TextField(); _tf.antiAliasType = 'advanced'; _tf.embedFonts = true; _tf.type = 'dynamic'; _tf.selectable = false; // textformat _tfmt = new TextFormat(); set(defaultParams); set(params); } public function get(param:String):Object { switch (param) { case 'size': return _tfmt.size; case 'text': return _tf.text; case 'font': return _tfmt.font; case 'color': return _tfmt.color; case 'background': return _tf.background; case 'backgroundColor': return _tf.backgroundColor; case 'width': return _tf.width; case 'height': return _tf.height; case 'multiline': return _tf.multiline; case 'wordWrap': return _tf.multiline; default: return this[param]; } return null; } public function set(params:Object):Object { for (var i:String in params) { setParam(i, params[i]); } redraw(); return this; } private function setParam(param:String, value:Object):Object { switch (param) { case 'size': _tfmt.size = new String(value); break; case 'text': _tf.text = new String(value); break; case 'font': _tfmt.font = new String(value); break; case 'color': _tfmt.color = new uint(value); break; case 'background': _tf.background = new Boolean(value); break; case 'backgroundColor': _tf.backgroundColor = new uint(value); break; case 'width': _tf.width = new Number(value); break; case 'height': _tf.height = new Number(value); break; case 'multiline': _tf.multiline = new Boolean(value); break; case 'wordWrap': _tf.multiline = new Boolean(value); break; default: this[param] = value; break; } return this; } private function redraw():void { _tf.setTextFormat(_tfmt); if (contains(_tf)) removeChild(_tf); if (_tf.width == 0) _tf.width= _tf.textWidth+5; _tf.height = _tf.textHeight; addChild(_tf); } } But when I do this: public class Main extends Sprite { public function Main() { addChild(new IskwabolText({ size: 100, text: 'iskwabol', font: 'Default', // this is properly embedded color: 0x000000, x: stage.stageWidth / 2 - this.width / 2, y: 140 })); } } The child IskwabolText doesn't get displayed. What happening?

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  • How to return relationships in a custom un-typed dataservice provider

    - by monkey_p
    I have a custom .Net DataService and can't figure out how to return the data for relationships. The data base has 2 tables (Customer, Address). A Customer can have multiple addresses, but each address can only have on customer. I'm using Dictionary<string,object> as my data type. My question, for the following 2 urls how do i return the data. http://localhost/DataService/Customer(1)/Address http://localhost/DataService/Address(1)/Customer For the none relational queries I return a List<Dictionary<string,object>> So I imagined for the relation I should just populate the element with a either a Dictionary<string,object> for the single ones and a List<Dictionary<string,object>> for many relationships. But this just gives me a NullRefferenceException So what am I doing wrong?

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  • Getting a substring in Ruby by x number of chars

    - by wotaskd
    I'm trying to produce some Ruby code that will take a string and return a new one, with a number x number of characters removed from its end - these can be actual letters, numbers, spaces etc. Ex: given the following string a_string = "a1wer4zx" I need a simple way to get the same string, minus - say - the 3 last digits. In the case above, that would be "a1wer". The way I'm doing it right now seems very convoluted: an_array = a_string.split(//,(a_string.length-2)) an_array.pop new_string = an_array.join Any ideas?

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  • What .NET UnmanagedType is Unicode (UTF-16)?

    - by Pat
    I am packing bytes into a struct, and some of them correspond to a Unicode string. The following works fine for an ASCII string: [StructLayout(LayoutKind.Sequential)] private struct PacketBytes { [MarshalAs(UnmanagedType.ByValTStr, SizeConst = 64)] public string MyString; } I assumed that I could do [StructLayout(LayoutKind.Sequential)] private struct PacketBytes { [MarshalAs(UnmanagedType.LPWStr, SizeConst = 32)] public string MyString; } to make it Unicode, but that didn't work. (Since this field is part of a struct with other fields, which I've omitted for clarity, I can't simply change the CharSet of the containing struct.) Any idea what I'm doing wrong?

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  • Rails: Serializing objects in a database?

    - by keruilin
    I'm looking for some general guidance on serializing objects in a database. What are serialized objects? What are some best-practice scenarios for serializing objects in a DB? What attributes do you use when creating the column in the DB so you can use a serialized object? How to save a serialized object? And how to access the serialized object and its attributes? (Using hashes?)

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  • singledispatch in class, how to dispatch self type

    - by yanxinyou
    Using python3.4. Here I want use singledispatch to dispatch different type in __mul__ method . The code like this : class Vector(object): ## some code not paste @functools.singledispatch def __mul__(self, other): raise NotImplementedError("can't mul these type") @__mul__.register(int) @__mul__.register(object) # Becasue can't use Vector , I have to use object def _(self, other): result = Vector(len(self)) # start with vector of zeros for j in range(len(self)): result[j] = self[j]*other return result @__mul__.register(Vector) # how can I use the self't type @__mul__.register(object) # def _(self, other): pass # need impl As you can see the code , I want support Vector*Vertor , This has Name error Traceback (most recent call last): File "p_algorithms\vector.py", line 6, in <module> class Vector(object): File "p_algorithms\vector.py", line 84, in Vector @__mul__.register(Vector) # how can I use the self't type NameError: name 'Vector' is not defined The question may be How Can I use class Name a Type in the class's method ? I know c++ have font class statement . How python solve my problem ? And it is strange to see result = Vector(len(self)) where the Vector can be used in method body .

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  • Unable to establish the connection to the file in BlackBerry

    - by Vikas
    I have tried the example code on SO to read the contents from the file in the resource directory in BlackBerry. But I am having an issue with the FileConnection. I get the following error: File system error (1003) I tried the example from here. I want only the read functionality, the file I want to read is in CSV format as a .txt file placed in the /res/test.txt. public class FileDemo extends MainScreen { public FileDemo() { setTitle("My Page"); String str = readTextFile("file:///test.txt"); System.out.println("Contents of the file::::::: " + str); } public String readTextFile(String fName) { String result = null; FileConnection fconn = null; DataInputStream is = null; try { fconn = (FileConnection) Connector.openInputStream(fName); is = fconn.openDataInputStream(); byte[] data = IOUtilities.streamToBytes(is); result = new String(data); } catch (IOException e) { System.out.println(e.getMessage()); } finally { try { if (null != is) is.close(); if (null != fconn) fconn.close(); } catch (IOException e) { System.out.println(e.getMessage()); } } return result; } } Any suggestions/advice on a better approach or as to how I can get this working??

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