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  • How do I write a writer method for a class variable in Ruby?

    - by tepidsam
    I'm studying Ruby and my brain just froze. In the following code, how would I write the class writer method for 'self.total_people'? I'm trying to 'count' the number of instances of the class 'Person'. class Person attr_accessor :name, :age @@nationalities = ['French', 'American', 'Colombian', 'Japanese', 'Russian', 'Peruvian'] @@current_people = [] @@total_people = 0 def self.nationalities #reader @@nationalities end def self.nationalities=(array=[]) #writer @@nationalities = array end def self.current_people #reader @@current_people end def self.total_people #reader @@total_people end def self.total_people #writer #-----????? end def self.create_with_attributes(name, age) person = self.new(name) person.age = age person.name = name return person end def initialize(name="Bob", age=0) @name = name @age = age puts "A new person has been instantiated." @@total_people =+ 1 @@current_people << self end

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  • How do I add an object to a binary tree based on the value of a member variable?

    - by Max
    How can I get a specific value from an object? I'm trying to get a value of an instance for eg. ListOfPpl newListOfPpl = new ListOfPpl(id, name, age); Object item = newListOfPpl; How can I get a value of name from an Object item?? Even if it is easy or does not interest you can anyone help me?? Edited: I was trying to build a binary tree contains the node of ListOfPpl, and need to sort it in the lexicographic. Here's my code for insertion on the node. Any clue?? public void insert(Object item){ Node current = root; Node follow = null; if(!isEmpty()){ root = new Node(item, null, null); return; }boolean left = false, right = false; while(current != null){ follow = current; left = false; right = false; //I need to compare and sort it if(item.compareTo(current.getFighter()) < 0){ current = current.getLeft(); left = true; }else { current = current.getRight(); right = true; } }if(left) follow.setLeft(new Node(item, null, null)); else follow.setRight(new Node(item, null, null)); }

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  • Wouldn't it be nice to have a type variable referring to the class's instance.

    - by user93197
    I often have a pattern like this: class VectorBase<SubClass, Element> where SubClass : VectorBase<SubClass, Element>, new() where Element : Addable<Element> { Element[] data; public VectorBase(Element[] data) { this.data = data; } public SubClass add(SubClass second) { Element[] newData = new Element[data.Length]; for (int i = 0; i < newData.Length; i++) { newData[i] = data[i].add(second.data[i]); } SubClass result = new SubClass(); result.data = newData; return result; } } class VectorInt : VectorBase<VectorInt, Int32> { } class MyInt : Addable<MyInt> { int data; public MyInt(int data) { this.data = data; } public MyInt add(MyInt t) { return new MyInt(data + t.data); } } interface Addable<T> { T add(T t); } But I would rather just have: class VectorBase2<Element> where Element : Addable<Element> { Element[] data; public VectorBase(Element[] data) { this.data = data; } public SubClass add(SubClass second) { Element[] newData = new Element[data.Length]; for (int i = 0; i < newData.Length; i++) { newData[i] = data[i].add(second.data[i]); } SubClass result = new SubClass(data); return result; } } class VectorInt2 : VectorBase2<Int32> { } Why not make the subclass type available to all classes? Is this technically impossible?

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  • Why "constructor-way" of declaring variable in "for-loop" allowed but in "if-statement" not allowed?

    - by PiotrNycz
    Consider this simple example: /*1*/ int main() { /*2*/ for (int i(7); i;){break;} /*3*/ if (int i(7)) {} /*4*/ } Why line-2 compiles just fine, whilst line-3 gives the error? This is little strange to me why if-statement is in this aspect treated worse than for-loop? If this is compiler specific - I tested with gcc-4.5.1: prog.cpp: In function 'int main()': prog.cpp:3:7: error: expected primary-expression before 'int' prog.cpp:3:7: error: expected ')' before 'int' I was inspired by this question [UPDATE] I know this compiles just fine: /*1*/ int main() { /*2*/ for (int i = 7; i;){break;} /*3*/ if (int i = 7) {} /*4*/ }

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  • Fetching only the first record in the table (via the view) without changing controller?

    - by bgadoci
    I am trying to only fetch the first record in my table for display. I am creating a site where a user can upload multiple images and attach to a post but I only want to display the first image view for each post. For further clarification posts belong_to projects. So when you are on the projects show page you see multiple posts. In this view I only want to display the first image for each post. Is there a way to do this in the view without affecting the controller (as later I want to allow users to browse all photos through the addition of a lightbox). Here is my /views/posts/_post.html.erb code: <% div_for post do %> <% post.photos.each do | photo | %> <%= image_tag(photo.data.url(:large), :alt => '') %> <%= photo.description %> <% end unless post.photos.first.new_record? rescue nil %> <%= link_to h(post.link_title), post.link %> <%= h(post.description) %> <%= link_to 'Manage this post', edit_post_path(post) %> <% end %> UPDATE: I am using a photos model to attach multiple photos to each post and using paperclip here.

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  • How can i use a variable created in a objective c Void function?

    - by James
    Im trying to get the lat and long values generated in a void function and use them within another function. Any help grateful. (void)locationManager:(CLLocationManager *)manager didUpdateToLocation:(CLLocation *)newLocation fromLocation:(CLLocation *)oldLocation { float latDeg = newLocation.coordinate.latitude; NSLog(@"Lat: %g", latDeg); float longDeg = newLocation.coordinate.longitude; NSLog(@"Lat: %g", longDeg); } I want to use the latDeg and longDeg variables.

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  • What is wrong in this simple Makefile

    - by Walidix
    SRC_VAR = test string for variable manipulation. TEST1_VAR = $(subset for,foo,${SRC_VAR}) all: @echo original str: ${SRC_VAR} @echo substitution: ${TEST1_VAR} This is the output: original str: test string for variable manipulation. substitution: The output should be: original str: My test string for variable manipulation. substitution: My test string foo variable manipulation.

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  • How to pass an integer to create new variable name?

    - by Joe
    I have 50 svg animations named animation0, animation1, animation2 etc. and I want to load them when the integer 0 to 49 is passed to this function: function loadAnimation(value){ var whichswiffy = "animation" + value; var stage = new swiffy.Stage(document.getElementById('swiffycontainer'), whichswiffy); stage.start(); } It doesn't work at the moment, maybe it's passing 'whichswiffy' rather than 'animation10'? Any ideas?

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  • How to declare a pointer to a variable as a parameter of a function in C++?

    - by Keand64
    I have a function that takes a pointer to a D3DXVECTOR3, but I have no reason to declare this beforehand. The most logical solution to me was using new: Function( //other parameters, new D3DXVECTOR3(x, y, 0)); but I don't know how I would go about deleting it, beign intitialized in a function. My next thought was to use the & operator, like so: Function( //other parameters, &D3DVECTOR3(x, y, 0)); but I don't know if this is a valid way to go about doing this. (It doesn't get an error, but neither does int *x; x = 50;). So should I use new, &, or some other technique I'm overlooking?

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  • What is the most "database independent" way of creating a variable length text field in a database

    - by Thibaut Colar
    I want to create a text field in the database, with no specific size (it will store text of length unknown in some case) - the particular text are serialized simple object (~ JSON) What is the most database independent way to do this : - a varchar with no size specified (don't think all db support this) - a 'text' field, this seems to be common, but I don't believe it's a standard - a blob or other object of that kind ? - a varchar of a a very large size (that's inefficient and wastes disk space probably) - Other ? I'm using JDBC, but I'd like to use something that is supported in most DB (oracle, mysql, postgresql, derby, HSQL, H2 etc...) Thanks.

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  • Is there a straightforward way to have a thread-local instance variable?

    - by Dan Tao
    With the ThreadStatic attribute I can have a static member of a class with one instance of the object per thread. This is really handy for achieving thread safety using types of objects that don't guarantee thread-safe instance methods (e.g., System.Random). It only works for static members, though. Is there any straightforward way to declare a class member as thread-local, meaning, each class instance gets an object per thread?

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  • What are possible suffixes after variable name in VBA?

    - by archimed7592
    As I've already figured out, there is at least six of them: !@#$%&. Here is snip: Dim A!, B@, C#, D$, E%, F& Debug.Print "A! - " & TypeName(A) Debug.Print "B@ - " & TypeName(B) Debug.Print "C# - " & TypeName(C) Debug.Print "D$ - " & TypeName(D) Debug.Print "E% - " & TypeName(E) Debug.Print "F& - " & TypeName(F) Outputs A! - Single B@ - Currency C# - Double D$ - String E% - Integer F& - Long Where is documentation on this syntax sugar? What other possible suffixes are there? Is there one for Date?

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  • How can I draw a line with a variable of width?

    - by user1729944
    #include <iostream> #include <cmath> #include "graph1.h" using namespace std; int main() { int diameter = 0; int height = 0; double rate = 0; char repeat = 'y'; int obj_num = 0; displayGraphics(); obj_num = drawRect(0,0,50,400); setColor(obj_num,200,200,200); obj_num = drawRect(0,400,640,79); setColor(obj_num,71,35,35); obj_num = drawLine(50,50,150,50,5); setColor(obj_num,80,80,80); displayBMP("faucet.bmp",150,12); do { do { cout << "Enter the diamater of the cylinder <in inches > 0 but <= 300: "; cin >> diameter; if((diameter<0) || (diameter>300)) { cout << "Incorrect diamater entered; value must be between 1 and 300" << endl; } }while((diameter<0) || (diameter>300)); do { cout << "Enter the height of the cylinder <in inches > 0 but <= 325: "; cin >> height; if((height<0) || (height>325)) { cout << "Incorrect height entered; value must be between 1 and 325" << endl; } }while((height<0) || (height>325)); do { cout << "Enter the facet water's rate: <gallons/minute> "; cin >> rate; if((rate<0) || (rate>100)) { cout << "Incorrect rate entered; value must be between 1 and 100" << endl; } }while((rate<0) || (rate>100)); //I need to draw the lines here. The graphics window has a faucet that is supposed to fill //up a cylinder made out of 3 lines. I don't know how to make the lines vary from the users //input since lines are hard coded with points and all i am receiving is the width for the //bottom line and the height for the left and right lines. cout << "Repeat program? (y/n): "; cin >> repeat; clearGraphics(); }while ( (repeat == 'y') || (repeat == 'Y') ); return 0; } Here is a screenshot for reference:

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  • jQuery: Quick question. How to select string variable?

    - by user317563
    Hello world, EDIT: I would like to avoid doing something like this: var str = 'Hello'; if ( str == 'Hello') { alert(str); } I would rather do: var str = 'Hello'; $(str).filter(':contains("Hello")').each(function(){ alert(this) }); I've tried a lot of things: $(str).text().method1().method2().method3(); $(str).val().method1().method2().method3(); $(str).contents().method1().method2().method3(); Nothing worked. Is it possible to do this? Thank you for your time. Kind regards, Marius

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  • Function to extract data in insert into satement for a table.

    - by user269484
    Hi...I m using this Function to extract the data but unable to extract LONG datatype. Can anyone help me? create or replace Function ExtractData(v_table_name varchar2) return varchar2 As b_found boolean:=false; v_tempa varchar2(8000); v_tempb varchar2(8000); v_tempc varchar2(255); begin for tab_rec in (select table_name from user_tables where table_name=upper(v_table_name)) loop b_found:=true; v_tempa:='select ''insert into '||tab_rec.table_name||' ('; for col_rec in (select * from user_tab_columns where table_name=tab_rec.table_name order by column_id) loop if col_rec.column_id=1 then v_tempa:=v_tempa||'''||chr(10)||'''; else v_tempa:=v_tempa||',''||chr(10)||'''; v_tempb:=v_tempb||',''||chr(10)||'''; end if; v_tempa:=v_tempa||col_rec.column_name; if instr(col_rec.data_type,'CHAR') 0 then v_tempc:='''''''''||'||col_rec.column_name||'||'''''''''; elsif instr(col_rec.data_type,'DATE') 0 then v_tempc:='''to_date(''''''||to_char('||col_rec.column_name||',''mm/dd/yyyy hh24:mi'')||'''''',''''mm/dd/yyyy hh24:mi'''')'''; else v_tempc:=col_rec.column_name; end if; v_tempb:=v_tempb||'''||decode('||col_rec.column_name||',Null,''Null'','||v_tempc||')||'''; end loop; v_tempa:=v_tempa||') values ('||v_tempb||');'' from '||tab_rec.table_name||';'; end loop; if Not b_found then v_tempa:='-- Table '||v_table_name||' not found'; else v_tempa:=v_tempa||chr(10)||'select ''-- commit;'' from dual;'; end if; return v_tempa; end; /

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  • How to run jQuery onClick? Need to pass a variable to run .ajax

    - by user205307
    I'm trying to run .ajax and insert a data element from the onClick of an item from the page. Whats the best way to do this? Something like this: function grabinfo(foo){ $.ajax({ url: "infospitter", method: "GET", data: "id="+foo, success: function(html){ $(#showstuff).html(html); } }); } <input onClick="javascript:grabinfo(18343)" /> // and on page each item will have this button input

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  • Assigning a pointer variable to a const int in C++?

    - by John
    I'm wondering if anyone can explain the following to me: If I write int i = 0; float* pf = i; I get a compile error (gcc 4.2.1): error: invalid conversion from ‘int’ to ‘float*’ Makes sense - they are obviously two completely different types. But if instead I write const int i = 0; float* pf = i; It compiles without error. Why should the 'const' make a difference on the right hand side of the assignment? Isn't part of the idea of the 'const' keyword to be able to enforce type constraints for constant values? Any explanation I have been able to come up with feels kind of bogus. And none of my explanations also explain the fact that const int i = 1; float* pf = i; fails to compile. Can anyone offer an explanation?

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