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  • No Method Error Undefined method 'save' for nil:NilClass

    - by BennyB
    I'm getting this error when i try to create a "Lecture" via my Lecture controller's create method. This used to work but i went on to work on other parts of the app & then of course i come back & something is now throwing this error when a user tries to create a Lecture in my app. I'm sure its something small i'm just overlooking (been at it a while & probably need to take a break)...but I'd appreciate if someone could let me know why this is happening...let me know if i need to post anything else...thx! The error I get NoMethodError in LecturesController#create undefined method `save' for nil:NilClass Rails.root: /Users/name/Sites/rails_projects/app_name Application Trace | Framework Trace | Full Trace app/controllers/lectures_controller.rb:13:in `create' My view to create a new Lecture views/lectures/new.html.erb <% provide(:title, 'Start a Lecture') %> <div class="container"> <div class="content-wrapper"> <h1>Create a Lecture</h1> <div class="row"> <div class="span 6 offset3"> <%= form_for(@lecture) do |f| %> <%= render 'shared/error_messages', :object => f.object %> <div class="field"> <%= f.text_field :title, :placeholder => "What will this Lecture be named?" %> <%= f.text_area :content, :placeholder => "Describe this Lecture & what will be learned..." %> </div> <%= f.submit "Create this Lecture", :class => "btn btn-large btn-primary" %> <% end %> </div> </div> </div> </div> Then my controller where its saying the error is coming from controllers/lectures_controller.rb class LecturesController < ApplicationController before_filter :signed_in_user, :only => [:create, :destroy] before_filter :correct_user, :only => :destroy def index end def new @lecture = current_user.lectures.build if signed_in? end def create if @lecture.save flash[:success] = "Lecture created!" redirect_to @lecture else @activity_items = [ ] render 'new' end end def show @lecture = Lecture.find(params[:id]) end def destroy @lecture.destroy redirect_to root_path end private def correct_user @lecture = current_user.lectures.find_by_id(params[:id]) redirect_to root_path if @lecture.nil? end

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  • Question regarding the method local innerclasses accesing the local variables of the method

    - by flash
    Hi I was going through the SCJP book about the innerclasses, and found this statement, it goes something like this. "A method local class can only refer to the local variables which are marked final" and in the explanation the reason specified is about the scope and lifetime of the local class object and the local variables on the heap, But I am unable to understand that.am I missing anything here about 'final'??

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  • How do I dispatch to a method based on a parameter's runtime type in C# < 4?

    - by Evan Barkley
    I have an object o which guaranteed at runtime to be one of three types A, B, or C, all of which implement a common interface I. I can control I, but not A, B, or C. (Thus I could use an empty marker interface, or somehow take advantage of the similarities in the types by using the interface, but I can't add new methods or change existing ones in the types.) I also have a series of methods MethodA, MethodB, and MethodC. The runtime type of o is looked up and is then used as a parameter to these methods. public void MethodA(A a) { ... } public void MethodB(B b) { ... } public void MethodC(C c) { ... } Using this strategy, right now a check has to be performed on the type of o to determine which method should be invoked. Instead, I would like to simply have three overloaded methods: public void Method(A a) { ... } // these are all overloads of each other public void Method(B b) { ... } public void Method(C c) { ... } Now I'm letting C# do the dispatch instead of doing it manually myself. Can this be done? The naive straightforward approach doesn't work, of course: Cannot resolve method 'Method(object)'. Candidates are: void Method(A) void Method(B) void Method(C)

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  • How to avoid general names for abstract classes?

    - by djechlin
    In general it's good to avoid words like "handle" or "process" as part of routine names and class names, unless you are dealing with (e.g.) file handles or (e.g.) unix processes. However abstract classes often don't really know what they're going to do with something besides, say, process it. In my current situation I have an "EmailProcessor" that logs into a user's inbox and processes messages from it. It's not really clear to me how to give this a more precise name, although I've noticed the following style matter arises: better to treat derived classes as clients and named the base class by the part of the functionality it implements? Gives it more meaning but will violate is-a. E.g. EmailAcquirer would be a reasonable name since it's acquiring for the derived class, but the derived class won't be acquiring for anyone. Or just really vague name since who knows what the derived classes will do. However "Processor" is still too general since it's doing many relevant operations, like logging in and using IMAP. Any way out of this dilemma? Problem is more evident for abstract methods, in which you can't really answer the question "what does this do?" because the answer is simply "whatever the client wants."

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  • Custom field names in Rails error messages

    - by Madhan ayyasamy
    The defaults in Rails with ActiveRecord is beautiful when you are just getting started and are created everything for the first time. But once you get into it and your database schema becomes a little more solidified, the things that would have been easy to do by relying on the conventions of Rails require a little bit more work.In my case, I had a form where there was a database column named “num_guests”, representing the number of guests. When the field fails to pass validation, the error messages is something likeNum guests is not a numberNot quite the text that we want. It would be better if it saidNumber of guests is not a numberAfter doing a little bit of digging, I found the human_attribute_name method. You can override this method in your model class to provide alternative names for fields. To change our error message, I did the followingclass Reservation ... validates_presence_of :num_guests ... HUMAN_ATTRIBUTES = { :num_guests = "Number of guests" } def self.human_attribute_name(attr) HUMAN_ATTRIBUTES[attr.to_sym] || super endendSince Rails 2.2, this method is used to support internationalization (i18n). Looking at it, it reminds me of Java’s Resource Bundles and Spring MVC’s error messages. Messages are defined based off a key and there’s a chain of look ups that get applied to resolve an error’s message.Although, I don’t see myself doing any i18n work in the near-term, it is cool that we have that option now in Rails.

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  • Is there an excuse for short variable names?

    - by KChaloux
    This has become a large frustration with the codebase I'm currently working in; many of our variable names are short and undescriptive. I'm the only developer left on the project, and there isn't documentation as to what most of them do, so I have to spend extra time tracking down what they represent. For example, I was reading over some code that updates the definition of an optical surface. The variables set at the start were as follows: double dR, dCV, dK, dDin, dDout, dRin, dRout dR = Convert.ToDouble(_tblAsphere.Rows[0].ItemArray.GetValue(1)); dCV = convert.ToDouble(_tblAsphere.Rows[1].ItemArray.GetValue(1)); ... and so on Maybe it's just me, but it told me essentially nothing about what they represented, which made understanding the code further down difficult. All I knew was that it was a variable parsed out specific row from a specific table, somewhere. After some searching, I found out what they meant: dR = radius dCV = curvature dK = conic constant dDin = inner aperture dDout = outer aperture dRin = inner radius dRout = outer radius I renamed them to essentially what I have up there. It lengthens some lines, but I feel like that's a fair trade off. This kind of naming scheme is used throughout a lot of the code however. I'm not sure if it's an artifact from developers who learned by working with older systems, or if there's a deeper reason behind it. Is there a good reason to name variables this way, or am I justified in updating them to more descriptive names as I come across them?

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  • calling Overloaded method from a generic method.

    - by asela38
    How to create a generic method which can call overloaded methods? I tried but it gives a compilation error. Test.java:19: incompatible types found : java.lang.Object required: T T newt = getCloneOf(t); ^ import java.util.*; public class Test { private Object getCloneOf(Object s) { return new Object(); } private String getCloneOf(String s) { return new String(s); } private <T> Set<T> getCloneOf(Set<T> set){ Set<T> newSet = null; if( null != set) { newSet = new HashSet<T>(); for (T t : set) { T newt = getCloneOf(t); newSet.add(newt); } } } }

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  • Ruby - Call method passing values of array as each parameter

    - by Markus Orreilly
    I'm currently stuck on this problem. I've hooked into the method_missing function in a class I've made. When a function is called that doesn't exist, I want to call another function I know exists, passing the args array as all of the parameters to the second function. Does anyone know a way to do this? For example, I'd like to do something like this: class Blah def valid_method(p1, p2, p3, opt=false) puts "p1: #{p1}, p2: #{p2}, p3: #{p3}, opt: #{opt.inspect}" end def method_missing(methodname, *args) if methodname.to_s =~ /_with_opt$/ real_method = methodname.to_s.gsub(/_with_opt$/, '') send(real_method, args) # <-- this is the problem end end end b = Blah.new b.valid_method(1,2,3) # output: p1: 1, p2: 2, p3: 3, opt: false b.valid_method_with_opt(2,3,4) # output: p1: 2, p2: 3, p3: 4, opt: true (Oh, and btw, the above example doesn't work for me)

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  • objective-c description method

    - by rocity
    Maybe I'm stupid...and this is my first question so forgive me...but when I run this code, I get the following output: (FROG idle:0 animating:0 rect:(null) position:{{1,2}{3,4}} tongue:{5,6}) This is wrong because it seems to be skipping the rect format string and placing everything displaced by one. So idle and animating are what i expect, then rect is skipped, but the result from NSStringFromCGRect(self.rect) is placed into position, then the result for position is pushed to tongue, then tongue is not displayed at all. I'm at a loss. - (NSString *)description{ return [NSString stringWithFormat:@"(FROG idle:%i animating:%i rect:%@ position:%@ tongue:%@)", self.idleTime, self.animating, NSStringFromCGRect(self.rect), NSStringFromCGPoint(self.position), tongue ]; }

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  • Passing parameters to web service method in c#

    - by wafa.cs1
    Hello I'm developing an android application .. which will send location data to a web service to store in the server database. In Java: I've used REST protocol so the URI is: HttpPost request = new HttpPost("http://trafficmapsa.com/GService.asmx/GPSdata? lon="+Lon+"&Lat="+Lat+"&speed="+speed); In Asp.net (c#) web service will be: [WebMethod] public CountryName GPSdata(Double Lon, Double Lat, Double speed) { after passing the data from android ..nothing return in back .. and there is no data in the database!! Is there any library missing in the CS file!! I cannot figure out what is the problem.

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  • Java synchronized method lock on object, or method?

    - by wuntee
    If I have 2 synchronized methods in the same class, but each accessing different variables, can 2 threads access those 2 methods at the same time? Does the lock occur on the object, or does it get as specific as the variables inside the synchronized method? Example: class x{ private int a; private int b; public synchronized void addA(){ a++; } public synchronized void addB(){ b++; } } Can 2 threads access the same instance of class x performing x.addA() and x.addB() at the same time?

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  • PHP OOP: Method Chaining

    - by Isis
    I have the following code, <?php class Templater { static $params = array(); public static function assign($name, $value) { self::$params[] = array($name => $value); } public static function draw() { self::$params; } } $test = Templater::assign('key', 'value'); $test = Templater::draw(); print_r($test); How can I alter this script so I could use this? $test = Templater::assign('key', 'value')->assign('key2', 'value2')->draw(); print_r($test);

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  • Hashing a python method to regenerate output when method is modified

    - by Seth Johnson
    I have a python method that has a deterministic result. It takes a long time to run and generates a large output: def time_consuming_method(): # lots_of_computing_time to come up with the_result return the_result I modify time_consuming_method from time to time, but I would like to avoid having it run again while it's unchanged. [Time_consuming_method only depends on functions that are immutable for the purposes considered here; i.e. it might have functions from Python libraries but not from other pieces of my code that I'd change.] The solution that suggests itself to me is to cache the output and also cache some "hash" of the function. If the hash changes, the function will have been modified, and we have to re-generate the output. Is this possible or a ridiculous idea? If this isn't a terrible idea, is the best implementation to write f = """ def ridiculous_method(): a = # # lots_of_computing_time return a """ , use the hashlib module to compute a hash for f, and use compile or eval to run it as code?

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  • mod_rewrite rule to work with get method

    - by Davi
    I'm using this rule: RewriteRule ^(.*)$ public/$1 [L] and in public folder I use: $url = $_GET['url']; when I try to acess something on url using slash or it works fine and I get: /cities/display/45 => Array ( [0] => cities [1] => display [2] => 45) But when I try to submit a form, i'm not able to acces the data: /cities/?field1=value1&field2=value2 => Array ( [0] => cities) How can I solve this? I need a rule that also gets form's submited values Thanks

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  • VSC++, virtual method at bad adress, curious bug

    - by antoon.groenewoud
    Hello, This guy: virtual phTreeClass* GetTreeClass() const { return (phTreeClass*)m_entity_class; } When called, crashed the program with an access violation, even after a full recompile. All member functions and virtual member functions had correct memory adresses (I hovered mouse over the methods in debug mode), but this function had a bad memory adress: 0xfffffffc. Everything looked okay: the 'this' pointer, and everything works fine up until this function call. This function is also pretty old and I didn't change it for a long time. The problem just suddenly popped up after some work, which I commented all out to see what was doing it, without any success. So I removed the virtual, compiled, and it works fine. I add virtual, compiled, and it still works fine! I basically changed nothing, and remember that I did do a full recompile earlier, and still had the error back then. I wasn't able to reproduce the problem. But now it is back. I didn't change anything. Removing virtual fixes the problem. Sincerely, Antoon

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  • Creating a method that is simultaneously an instance and class method

    - by Mike Axiak
    In Python, I'd like to be able to create a function that behaves both as a class function and an instance method, but with the ability to change behaviors. The use case for this is for a set of serializable objects and types. As an example: >>> class Thing(object): #... >>> Thing.to_json() 'A' >>> Thing().to_json() 'B' I know that given the definition of classmethod() in funcobject.c in the Python source, this looks like it'd be simple with a C module. Is there a way to do this from within python? Thanks!

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  • C++, create an instance from a static method

    - by Manux
    Hello, let's say I want my users to use only one class, say SpecialData. Now, this data class would have many methods, and depending on the type of data, the methods do different things, internally, but return externally similar results. Therefore my wanting to have one "public" class and other "private", child classes that would change the behavior of methods, etc... It would be amazingly more simple for some types of data that need to be built to do something like this: SpecialData& sm = SpecialData::new_supermatrix(); and new_supermatrix() would return a SuperMatrix instance, which inherits from most behaviors of SpecialData. my header: static SpecialData& new_supermatrix(); my cpp: SpecialData& SpecialData::new_supermatrix()(){ return SuperMatrix(MATRIX_DEFAULT_MAGNITUDE,1000,1239,FLOAT32,etc...); } The problem is, I get this error, which is probably logical due to the circumstances: invalid initialization of non-const reference of type ‘SpecialData&’ from a temporary of type ‘SpecialData’ So, any ideas?

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  • PHP OOP: method?

    - by Isis
    Hello <?php class Templater { static $params = array(); public static function assign($name, $value) { self::$params[] = array($name => $value); } public static function draw() { self::$params; } } $test = Templater::assign('key', 'value'); $test = Templater::draw(); print_r($test); How to alter this script so I could use this:? $test = Templater::assign('key', 'value')->assign('key2', 'value2')-draw(); print_r($test);

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  • Method to register method to be called when event is raised

    - by zaidwaqi
    I have a Panel which contains 20 PictureBox controls. If a user clicks on any of the controls, I want a method within the Panel to be called. How do I do this? public class MyPanel : Panel { public MyPanel() { for(int i = 0; i < 20; i++) { Controls.Add(new PictureBox()); } } // DOESN'T WORK. // function to register functions to be called if the pictureboxes are clicked. public void RegisterFunction( <function pointer> func ) { foreach ( Control c in Controls ) { c.Click += new EventHandler( func ); } } } How do I implement RegisterFunction()? Also, if there are cool C# features that can make the code more elegant, please share.

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  • Oracle Unified Method (OUM) Release 5.6

    - by user714714
    ORACLE® UNIFIED METHOD RELEASE 5.6 Oracle’s Full Lifecycle Methodfor Deploying Oracle-Based Business Solutions About | Release | Access | Previous Announcements About Oracle is evolving the Oracle® Unified Method (OUM) to achieve the vision of supporting the entire Enterprise IT Lifecycle, including support for the successful implementation of every Oracle product. OUM replaces Legacy Methods, such as AIM Advantage, AIM for Business Flows, EMM Advantage, PeopleSoft's Compass, and Siebel's Results Roadmap. OUM provides an implementation approach that is rapid, broadly adaptive, and business-focused. OUM includes a comprehensive project and program management framework and materials to support Oracle's growing focus on enterprise-level IT strategy, architecture, and governance. Release OUM release 5.6 provides support for Application Implementation, Cloud Application Implementation, and Software Upgrade projects as well as the complete range of technology projects including Business Intelligence (BI) and Enterprise Performance Management (EPM), Enterprise Security, WebCenter, Service-Oriented Architecture (SOA), Application Integration Architecture (AIA), Business Process Management (BPM), Enterprise Integration, and Custom Software. Detailed techniques and tool guidance are provided, including a supplemental guide related to Oracle Tutor and UPK. This release features: Business Process Management (BPM) Project Engineering Supplemental Guide Cloud Roadmap View and Supplemental Guide Enterprise Security View and Supplemental Guide Service-Oriented Architecture (SOA) Governance Implementation Supplemental Guide "Tailoring OUM for Your Project" White Paper OUM Microsoft Project Workplan Template and User's Guide Mappings: OUM to J.D. Edwards OneMethodology, OUM Roles to Task Techniques: Determining Number of Iterations, Managing an OUM Project using Scrum Templates: Scrum Workplan (WM.010), Siebel CRM Enhanced / Updated: Manage Focus Area reorganized by Activities for all Views Oracle Architecture Development Process (OADP) View updated for OADP v3.0 Oracle Support Services Supplemental Guide expanded to include guidance related to IT Change Management Oracle User Productivity Kit Professional (UPK Pro) and Tutor Supplemental Guide expanded guidance for UPK Pro Service-Oriented Architecture (SOA) Application Integration Architecture (AIA) Supplemental Guide updated for SOA Tactical Project Delivery View Service-Oriented Architecture (SOA) Tactical Project Delivery View expanded to include additional tasks Siebel CRM Supplemental Guide expanded task guidance and added select Siebel-specific OUM templates WebCenter View and Supplemental Guide updated for WebCenter Portal and Content Management For a comprehensive list of features and enhancements, refer to the "What's New" page of the Method Pack. Upcoming releases will provide expanded support for Oracle's Enterprise Application suites including product-suite specific materials and guidance for tailoring OUM to support various engagement types. Access Oracle Customers Oracle customers may obtain copies of the method for their internal use – including guidelines, templates, and tailored work breakdown structure – by contracting with Oracle for a consulting engagement of two weeks or longer and meeting some additional minimum criteria. Customers, who have a signed consulting contract with Oracle and meet the engagement qualification criteria, are permitted to download the current release of OUM for their perpetual use. They may also obtain subsequent releases published during a renewable, three-year access period. Training courses are also available to these customers. Contact your local Oracle Sales Representative about enrolling in the OUM Customer Program. Oracle PartnerNetwork (OPN) Diamond, Platinum, and Gold Partners OPN Diamond, Platinum, and Gold Partners are able to access the OUM method pack, training courses, and collateral from the OPN Portal at no additional cost: Go to the OPN Portal at partner.oracle.com. Select the "Partners (Login Required)" tab. Login. Select the "Engage with Oracle" tab. From the Engage with Oracle page, locate the "Applications" heading. From the Applications heading, locate and select the "Oracle Unified Method" link. From the Oracle Unified Method Knowledge Zone, select the "Implement" tab. From the Implement tab, select the "Tools and Resources" link. Locate and select the "Oracle Unified Method (OUM)" link. Previous Announcements Oracle Unified Method (OUM) Release 5.6 Oracle Unified Method (OUM) Release 5.5 Oracle Unified Method (OUM) Release 5.4 Oracle EMM Advantage Retired Retirement of Oracle EMM Advantage Planned for December 01, 2011

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  • Method binding to base method in external library can't handle new virtual methods "between"

    - by Berg
    Lets say I have a library, version 1.0.0, with the following contents: public class Class1 { public virtual void Test() { Console.WriteLine( "Library:Class1 - Test" ); Console.WriteLine( "" ); } } public class Class2 : Class1 { } and I reference this library in a console application with the following contents: class Program { static void Main( string[] args ) { var c3 = new Class3(); c3.Test(); Console.ReadKey(); } } public class Class3 : ClassLibrary1.Class2 { public override void Test() { Console.WriteLine("Console:Class3 - Test"); base.Test(); } } Running the program will output the following: Console:Class3 - Test Library:Class1 - Test If I build a new version of the library, version 2.0.0, looking like this: public class Class1 { public virtual void Test() { Console.WriteLine( "Library:Class1 - Test V2" ); Console.WriteLine( "" ); } } public class Class2 : Class1 { public override void Test() { Console.WriteLine("Library:Class2 - Test V2"); base.Test(); } } and copy this version to the bin folder containing my console program and run it, the results are: Console:Class3 - Test Library:Class1 - Test V2 I.e, the Class2.Test method is never executed, the base.Test call in Class3.Test seems to be bound to Class1.Test since Class2.Test didn't exist when the console program was compiled. This was very surprising to me and could be a big problem in situations where you deploy new versions of a library without recompiling applications. Does anyone else have experience with this? Are there any good solutions? This makes it tempting to add empty overrides that just calls base in case I need to add some code at that level in the future...

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  • calling asp.net mvc action method using jquery post method expires the session

    - by nccsbim071
    hi, i have a website where i provicde a link. On clicking the link a controller action method is called to generate a zip file after creation of zip file is done, i show the link to download the zip file by replacing the link to create a zip with the link to download the zip. the problem is that after zip file creation is over and link is shown, when user clicks on the link to download the zip file, they are sent to login. After providing correct credentials in the login page they are prompted to download the zip file. they sould not be sent to the login page. In the action to generate zip file i haven't abondoned the session or haven't not done anything that abondons the session. the user should not be sen't to login page after successful creation of zip file user should be able to download the file without login. i search internet on this problem, but i did not find any solution. In one of the blog written by hanselman i found this statement that creates the problem with the session: Is some other thing like an Ajax call or IE's Content Advisor simultaneously hitting the default page or login page and causing a race condition that calls Session.Abandon? (It's happened before!) so i thought there might be some problem with ajax call that causes the session to expire, but i don't know what is happening? any help please thanks

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