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• Why people define class, trait, object inside another object in Scala?

  - by Zwcat

  Ok, I'll explain why I ask this question. I begin to read Lift 2.2 source code these days. In Lift, I found that, define inner class and inner trait are very heavily used. object Menu has 2 inner traits and 4 inner classes. object Loc has 18 inner classes, 5 inner traits, 7 inner objects. There're tons of codes write like this. I wanna to know why the author write it like this. Is it because it's the author's personal taste or a powerful use of language feature?

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• Rails - How to secure foreign keys and still allow association selection

  - by Bryce

  For simplicity, assume that I have a simple has-many-through relationship class User < ActiveRecord::Base has_many :courses, :through => :registrations end class Registration < ActiveRecord::Base belongs_to :user belongs_to :course end class Course < ActiveRecord::Base has_many :users, :through => :registrations end I want to keep my app secure, so I use attr_accessible to whitelist my attributes. My question is twofold: How would I set up my whitelist attributes such that I could create a new Registration object through a form (passing in :user and :course, but not risk allowing those foreign keys to be maliciously updated later? How would I set up my validations such that both belongs_to associations are required BUT also allow for Registration objects to be created in nested forms?

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• Is map/collection order stable between calls?

  - by John

  If I have a hash map and iterate over the objects repeatedly, is it correct that I'm not guaranteed the same order for every call? For example, could the following print two lines that differ from each other: Map<String,Integer> map = new HashMap<String,Integer>() {{ put("a", 1); put("b", 2); put("c", 3); }}; System.out.println(map); System.out.println(map); And is this the case for sets and collections in general? If so, what's the best way in case you have to iterate twice over the same collection in the same order (regardless of what order that is)? I guess converting to a list.

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• What does -setPropagatesDeletesAtEndOfEvent: actually do?

  - by dontWatchMyProfile

  Let me try it: If I don't set this, then the default value is YES. So when I delete an managed object from the context, the context propagates this immediately to the persistent store so the object is gone? And when I set this to NO, then objects are deleted from the persistent store only when calling -save? Is that really true? I mean: If it was true, then the default behavior is that once you call the context to delete an object, the object is gone. Lets assume you're not using an undo manager. So... gone. Right? No rollback possible? Or can it still be recovered with a rollback?

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• Python: UTF-8 problems (again...)

  - by blahblah

  I have a database which is synchronized against an external web source twice a day. This web source contains a bunch of entries, which have names and some extra information about these names. Some of these names are silly and I want to rename them when inserting them into my own database. To rename these silly names, I have a standard dictionary as such: RENAME_TABLE = { "Wsird" : "Weird", ... } As you can see, this is where UTF-8 comes into play. This is the function which performs renaming of all the problematic entries: def rename_all_entries(): all_keys = RENAME_TABLE.keys() entries = Entry.objects.filter(name__in=all_keys) for entry in entries: entry.name = RENAME_TABLE[entry.name] entry.save() So it tries to find the old name in RENAME_TABLE and renames the entry if found. However, I get a KeyError exception when using RENAME_TABLE[entry.name]. Now I'm lost, what do I do? I have... # -*- coding: utf-8 -*- ...in the top of the Python file.

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• Many-to-Many Relationship (with properties) in Google App Engine for Java

  - by rvandervort

  I understand from the official documentation on unowned relationships that the app must use sets of Key objects on either side of the relationship. This makes perfect sense. Coming from many years of RDBM-style programming, though, I'm pretty confused about how I can model properties of that relationship itself. For example, if I have entities Category and Entry in my many-to-many relationship and would like to persist a dateAdded property, or some other data that are only relevant when both sides of the relationship are known. I suppose it would be possible to create a third class : CategoryEntry that links the two, but this seems like a kludge. What is the proposed way to model this kind of situation ?

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• Calling inheriting class methods via interface.

  - by Stacey

  Given the scenario... interface IBase{ void Process(int value); } abstract class Base : IBase { public virtual void Process(int value){ throw new NotImplementedException(); } } class Implemented: Base, IBase { public void Process(int value) { // .. some code here.. } } I'm trying to write a loop similar to the following. foreach( Base b in CollectionOfImplemented ) { b.Process( // something will go here // ); } Trying this, it keeps calling Base.Process, instead of Implemented.Process; but the type in the collection is Implemented, not Base. Boxing it seems to work, but I was hoping to see if I could find a more intelligent approach to it, since the Collection will contain other types of objects that also inherit from Base.

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• Count function calls by name or signature. Gcc, C++

  - by MajesticRa

  I have some c++ written package. Linux, gcc. I can modify compilation process (change Makefile, flags, etc.), but can not change C++ source code. One runs the package with different parameters, it does a job and exits. How to count: 1) Number of calls of function with specific name? 2) Number of calls of functions with specific signature? 3) Number of calls of functions where one of the parameters is of specific type i.e. std::string (type is specified by signature)? 4) and extra Number of calls of functions of STL objects, i.e. std::string copy constructor? (I mean count a number of calls during the run. ) I thought to do it with GDB, but I found it very tough to do (1) and have not found how to do (2)-(4) at all. All acceptable answers I will write here for humanity.

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• How do I change the background image of my app?

  - by user356387

  Hello I have looked around and found some code which so called chooses an image from an array of image objects, but cant find an explanation. I would like to make my app have a background image and the user can select next and previous buttons to scroll through some full screen images, setting them as the background image as they scroll. I know how to do this in java, but cant seem to do it for this app. How or what code is linked to a next button to grab the next image in the array and reverse for the back button? Then that needs to be displayed obviously. I have used a layered architecture with a MVC style approach but cant seem to put it together with Objective-C. Would the buttons call the appropriate methods of the so called delegates, which the delegates handle fetching and returning the Images? Would the buttons use the returned images and actually handle the redrawing? I would really appreciate the help. Regards Jarryd

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• Java synchronizing static list ?

  - by JavaUser

  Hi, In a Java class , i am having a static list so this list is shared across all the objects of this class.The business logic in this class will run periodically which is invoked by some method with out passing instance parameters.Now I want to invoke this run method based on the list(I will add some vales into this list based on JMS) ,this list may empty sometimes and after finishing the run , i am emptying this list.Now my question is , whether I need to synchronize this list or not? Also let me know is there any other way to pass value in one object instance(Thread1) to other object instance (Thread2) other than having Static variable(static list)? Thx

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• Bind to a collection's view and just call ToString()

  - by womp

  I'm binding a GridView to a collection of objects that look like this: public class Transaction { public string PersonName { get; set; } public DateTime TransactionDate { get; set; } public MoneyCollection TransactedMoney { get; set;} } MoneyCollection simply inherits from ObservableCollection<T>, and is a collection of MyMoney type object. In my GridView, I just want to bind a column to the MoneyCollection's ToString() method. However, binding it directly to the TransactedMoney property makes every entry display the text "(Collection)", and the ToString() method is never called. I understand that it is binding to the collection's default view. So my question is - how can I make it bind to the collection in such a way that it calls the ToString() method on it? This is my first WPF project, so I know this might be a bit noobish, but pointers would be very welcome.

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• is this possible: c# collection of Type with constrains, or collection of generic type?

  - by Jon

  I'm trying to store types in a collection, so that i can later instantiate objects of the types in the collection. But I'm not sure how to do this the best way. What i have so far: List<Type> list = new List<Type>(); list.Add(typeof(MyClass)); var obj = (MyClass)Activator.CreateInstance(list[0]); I would like to have some constrains on the Type, or better yet, just a generic type in the collection instead of an instantiated Type object. Is this possible?

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• Lambda "if" statement?

  - by AndyC

  I have 2 objects, both of which I want to convert to dictionarys. I use toDictionary<(). The lambda expression for one object to get the key is (i = i.name). For the other, it's (i = i.inner.name). In the second one, i.name doesn't exist. i.inner.name ALWAYS exists if i.name doesn't. Is there a lambda expression I can use to combine these two? Basically to read as: "if i.name exists then set id to i.name, else set id to i.inner.name". Many thanks.

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• updating the values in detail view from another view....

  - by praseed

  Hi friends, i am building one app almost similar to contact management system...in which i have a detail view .. on pressing one of the table cells, a new view will be shown were the user can enter the new values and on pressing the save button the values will be updated in the database. On going back to the detail view the user should be able to see the updated values in the table cells.. or how can i update the values in detail view from another view...? i came to know that this can be acheived through Appdelegate objects ... but i couldnt understand wat is it or how it is done.... may be bcuz i am new to iPhone apps development... Pls can anyone explain me the process..

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• Using temporary arrays to cut down on code - inefficient?

  - by tommaisey

  I'm new to c++ (and SO) so sorry if this is obvious. I've started using temporary arrays in my code to cut down on repetition and to make it easier to do the same thing to multiple objects. So instead of: MyObject obj1, obj2, obj3, obj4; obj1.doSomming(arg); obj2.doSomming(arg); obj3.doSomming(arg); obj4.doSomming(arg); I'm doing: MyObject obj1, obj2, obj3, obj4; MyObject* objs[] = {&obj1, &obj2, &obj3, &obj4}; for (int i = 0; i !=4; ++i) objs[i]->doSomming(arg); Is this detrimental to performance? Like, does it cause unnecessary memory allocation? Is it good practice? Thanks.

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• java.util.Observable, will clients complete executing their update() before continuing

  - by jax

  When I call: setChanged(); notifyObservers() on a java.until.Observable class, will all the listening Observer objects complete execution of their udpate() methods - assuming we are running in the same Thread - before the java.until.Observable class continues running? This is important because I will be sending a few messages through the notifyObservers(Object o) method in quick concession, it is important that each Observer class has finished its method before the new one though. I understand that the order of execution for each Observer class may vary when we call notifyObservers() - it is just important that the order of method execution for each individual instance is in order.

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• JQuery - How do I count the number of elements selected by a selector?

  - by Josh

  I am using $().fadeOut() to fade items out in a list ( < li < /li). When the list is empty I wish to hide a parent object. I plan on doing this by checking in my trigger event that fades the list if the count of the objects is 0 then hide the parent element. I can use the fadeOut callback to remove the elements if necessary. The to the point question: How do I select li tags inside a ul and then get the total count of them using jquery?

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• What machine learning algorithms can be used in this scenario?

  - by ExceptionHandler

  My data consists of objects as follows. Obj1 - Color - shape - size - price - ranking So I want to be able to predict what combination of color/shape/size/price is a good combination to get high ranking. Or even a combination could work like for eg: in order to get good ranking, the alg predicts best performance for this color and this shape. Something like that. What are the advisable algorithms for such a prediction? Also may be if you can briefly explain how I can approach towards the model building I would really appreciate it. Say for eg: my data looks like Blue pentagon small $50.00 #5 Red Squre large $30.00 #3 So what is a useful prediction model that I should look at? What algorithm should I try to predict like say highest weightage is for price followed by color and then size. What if I wanted to predict in combinations like a Red small shape is less likely to higher rank compared to pink small shape . (In essence trying to combine more than one nominal values column to make the prediction)

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• syntax problem crating a method that returns an object (java)

  - by David

  I'm trying to create a method that will sum two timeO objects and return a new TimeO object called sum. Here is the relevant code snippet: public static TimeO add (TimeO t1, TimeO t2) { TimeO sum = new TimeO ; ... } When i try to compile it i get this error message: TimeO.java:15: '(' or '[' expected TimeO sum = new TimeO ; ^ 1 error i cant think of any reason why it would want me to open a set of parenthasies or brackets here but its possible that i dont' quite understand the syntax. Whats going wrong here?

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• Serialize object from within

  - by Maximus

  I have the class testClass which has the method save. This method saves object to a database. But it needs to serialize object before saving. How can I serialize object from within the class to do that? class testClass { private $prop = 777; public function save() { $serializedObject = serialize(self); DB::insert('objects', array('id', 'object')) ->values(array(1, $serializedObject)) ->execute(); } } serialize(self) obviously doesn't work.

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• Makefile won't copy .o to obj/ and target to bin/ folders

  - by about blank

  I'm trying to write a Makefile which will copy its target and objects to bin/ and obj/ directories, respectively. Yet, when I try to run it I get the following error: nasm -f elf64 -g -F stabs main.asm -l spacelander.lst ld -o spacelander obj/main.o ld: cannot find obj/main.o: No such file or directory make: *** [spacelander] Error 1 Why is this happening? Update I noticed when I posted the error that it was due to white spacing errors. After taking care of those, I still get the new error I replaced with the old one I mentioned prior. What is this?? Update 2 Posted -d flag output below Makefile source. Source ASM := nasm ARGS := -f FMT := elf64 OPT := -g -F stabs SRC := main.asm OBJDIR := obj TARGETDIR := bin OBJ := $(addprefix $(OBJDIR)/,$(patsubst %.asm, %.o, $(wildcard *.asm))) TARGET := spacelander .PHONY: all clean all: $(OBJDIR) $(TARGET) $(OBJDIR): mkdir $(OBJDIR) $(OBJDIR)/%.o: $(SRC) $(ASM) $(ARGS) $(FMT) $(OPT) $(SRC) -l $(TARGET).lst $(TARGET): $(OBJ) ld -o $(TARGET) $(OBJ) clean: @rm -f $(TARGET) $(wildcard *.o) @rm -rf $(OBJDIR) make -d Output - NOTE: output is too many characters for body, thus is pastebinned http://pastebin.com/3bctGJxs

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• Is this the right way of handling command line arguments?

  - by shadyabhi

  ask_username = True ask_password = True ask_message = True ask_number = True def Usage(): print '\t-h, --help: View help' print '\t-u, --username: Username' print '\t-p, --password: Password' print '\t-n, --number: numbber to send the sms' print '\t-m, --message: Message to send' sys.exit(1) opts, args = getopt(sys.argv[1:], 'u:p:m:n:h',["username=","password=","message=","number=","help"]) print opts, args for o,v in opts: if o in ("-h", "--help"): Usage() elif o in ("-u", "--username"): username = v ask_username = False elif o in ("-p", "--password"): passwd = v ask_password = False elif o in ("-m", "--message"): message = v ask_message = False elif o in ("-n", "--number"): number = v ask_number = False #Credentials taken here if ask_username: username = raw_input("Enter USERNAME: ") if ask_password: passwd = getpass() if ask_message: message = raw_input("Enter Message: ") if ask_number: number = raw_input("Enter Mobile number: ") I dont think it is, because I am using 4 objects just for checking if command line argument was provided... Guide me with the best way of doing it..

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• How much Java should I have learnt before trying Android programming?

  - by Sidney Yin

  Hi - I have been seeking beginner learning books in Android, and of course found out that I should learn Java first. So I began studying Java and now I am quite comfortable with objects, classes, inheritance, interfaces, and just moved onto Layouts in Swing as well as Swing Features. But I am starting to wonder.... do I know enough about Java now? Can I start programming Android yet? Of course I can keep going in Java, but have been itching to begin programming Android apps. Any definitive answer here about how much Java I need to know before Android? Thanks so much!

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• How to invoke a Servlet (doGet) in a web application on startup?

  - by Dan

  I need to invoke a Servlet on application startup since it contains some application initialization logic. I know I can set load-on-startup configuration, but this will only invoke Servlet’s init method. I need to invoke a doGet method and pass some Url parameters to it. Servlet doGet method expects ServletRequest and ServletResponse objects. Also, since this is clustered application, I need to know exactly what node I am accessing (since one option is just to open a socket and invoke a Servlet). What is the best option to perform this?

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• Getting the last member of a group on an intermediary M2M

  - by rh0dium

  If we look at the existing docs, what is the best way to get the last member added? This is similar to this but what I want to do is to be able to do this. group = Group.objects.get(id=1) group.get_last_member_added() #This is by ('-date_added') <Person: FOO> I think the best way is through a manager but how do you do this on an intermediary model? class Person(models.Model): name = models.CharField(max_length=128) def __unicode__(self): return self.name class Group(models.Model): name = models.CharField(max_length=128) members = models.ManyToManyField(Person, through='Membership') def __unicode__(self): return self.name class Membership(models.Model): person = models.ForeignKey(Person) group = models.ForeignKey(Group) date_joined = models.DateField() invite_reason = models.CharField(max_length=64)

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