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  • Ruby/Rails - Add records to an object with each loop iteration / Object vs Arrays

    - by ChrisWesAllen
    I'm trying to figure out how to add records to an existing object for each iteration of a loop. I'm having a hard time discovering the difference between an object and an array. I have this @events = Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops @events = Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end I'm trying to add a new events to the existing @events object based on the id of whatever the loop variable is. But the ( = ) operator just creates a new instance of the @events object. I tried ( += ) and ( << ) as operators but got the error "You have a nil object when you didn't expect it! You might have expected an instance of Array. The error occurred while evaluating nil" I tried created an array events = [] events << Event.find(1) @loops = Choices.find(:all, :limit => 5) #so loop for 5 instances of choice model for loop in @loops events << Event.find(:all,:conditions => ["event.id = ?", loop.event_id ]) end But I dont know how to call that arrays attributes within the view With objects I was able do create a loop within the view and call all the attributes of that object as well... <table> <% for event in @events %> <tr> <td><%= link_to event.title, event %></td> <td><%= event.start_date %></td> <td><%= event.price %></td> </tr> <% end %> </table> How could i do this with an array set? So the questions are 1) Whats the difference between arrays and objects? 2) Is there a way to add into the existing object for each iteration? 3) If I use an array, is there a way to call the attributes for each array record within the view?

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  • How do LL(*) parsers work?

    - by freezer878
    I cannot find any complete description about LL(*) parser, such as ANTLR, on Internet. I'm wondering what is the difference between an LL(k) parser and an LL(*) one and why they can't support left-recusrive grammars despite their flexibility.

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  • SQL INSERT performance omitting field names?

    - by Marco Demaio
    Does anyone knows if removing the field names from an INSERT query results in some performance improvements? I mean is this: INSERT INTO table1 VALUES (value1, value2, ...) faster for DB to be accomplished rather than doing this: INSERT INTO table1 (field1, field2, ...) VALUES (value1, value2, ...) ? I know it might be probably a meaningless performance difference, but just to know.

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  • iPhone memory management, a newbie question

    - by Reuven
    Hi, I've seen in (Apple) sample code two types of ways of allocation memory, and am not sure I understand the difference and resulting behavior. // FAILS NSMutableArray *anArray = [NSMutableArray array]; [anArray release]; // WORKS NSMutableArray *anArray1 = [[NSMutableArray alloc] init]; [anArray release]; By "FAILS" I mean I get crashes/runtime warnings etc., and not always as soon as I call the release... Any explanation appreciated. Thanks

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  • Eclipse's Visual Studio Ctrl+Tab and Ctrl+Shift+Tab Equivalent

    - by jasonh
    In Visual Studio, I always use Ctrl+Tab and Ctrl+Shift+Tab to navigate between documents. I see that Eclipse has Ctrl+F6 to navigate between editors, but this isn't nearly the same behavior. The difference being, pressing it once and then again will get you moving back and forth between two files, whereas in VS, it will cause you to navigate forward based on the tab order in the editor. Any ideas on how I can replicate VS's behavior?

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  • diffing two databases

    - by flybywire
    Is there a tool to find the difference between two databases. Both the schema and the actual data are pretty much the same, but not 100%. Do you know a tool that can help to succinctly describe the changes.

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  • Why would it be necessary to subclass from object in Python?

    - by rmh
    I've been using Python for quite a while now, and I'm still unsure as to why you would subclass from object. What is the difference between this: class MyClass(): pass And this: class MyClass(object): pass As far as I understand, object is the base class for all classes and the subclassing is implied. Do you get anything from explicitly subclassing from it? What is the most "Pythonic" thing to do?

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  • Generics : List<? extends Animal> is same as List<Animal>?

    - by peakit
    Hi, I am just trying to understand the extends keyword in Java Generics. List<? extends Animal> means we can stuff any object in the List which IS A Animal then won't the following also mean the same thing: List<Animal> Can someone help me know the difference between the above two? To me extends just sound redundant here. Thanks!

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  • How does a parser LL(*) works?

    - by freezer878
    Hi, I cannot find any complete description about LL() parser, such as ANTLR, on Internet. I'm wondering what is the difference between an LL(k) parser and an LL() one and why they can't support left-recusrive grammars despite their flexibility. Thanks in advance. Fabio.

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  • Testing for validity

    - by Konrad
    Hi, I'd like to know the difference (if any) between the following: if( someDOMElement.someProperty ) { ... if( someDOMElement.someProperty != null ) { ... if( someDOMElement.someProperty != undefined ) { ... Is one safer than the others?

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  • Static variables in C and C++

    - by Naveen
    Is there any difference between a variable declared as static outside any function between C and C++. I read that static means file scope and the variables will not be accessible outside the file. I also read that in C, global variables are static . So does that mean that global variables in C can not be accessed in another file?

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  • How to subtract dates in YYYYMMDD format?

    - by NinjaBomb
    I have 2 integer fields that represent dates in the YYYYMMDD format. What is the best way to subtract 2 of these fields to get the correct # of days between them? For instance, if I take the difference between 20100511 and 20100428 I would like the result to be 13 and not 83. I know I need to convert the integer fields into date formats but everything I have tried either throws an exception or doesn't work correctly. What am I missing? Answers in vb.net please

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  • VB.NET Function Return

    - by waves
    In order to return a value from a VB.NET function one can assign a value to the "Functions Name" or use "return value." I sometimes see these inter-mixed in the same function. Personally, I prefer the return. My question is, what is the internal difference, if any, between the two?

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