Forgive me if I'm being obtuse, but I'm a little bit confused by the documentation about nil in Clojure. It says:
nil has the same value as Java null.
Does this mean that they're the same thing or are they different somehow? And does a NullPointerException mean that a Java null was encountered or would I also get this if nil was ...
Title says it all I guess.
Is there anything wrong with doing something like
NSString * string = [ [ NSString alloc ] init ];
...
[ string release ];
or is there any value (other than best practice) in also adding
string = nil;
?
...
I find myself repeatedly looking for a clear definition of the differences of nil?, blank?, and empty? in Ruby on Rails. Here's the closest I've come:
blank? objects are false, empty, or a whitespace string. For example, "", " ", nil, [], and {} are blank.
nil? objects are instances of NilClass.
empty? objects are class-specific, and...
I've just been bitten by an annoying bug that was made obscure by the "send message to nil is ok" behaviour in Objective-C.
I've seen http://stackoverflow.com/questions/156395/sending-a-message-to-nil, and the consensus seems to be 'thats how we roll' in Objective-C.
Now, maybe I don't have enough experience in Objective-C, but it seem...
I have a very annoying and hard to figure out bug in my rails project.
After having created a bunch of models and their relations, I want to list them.
But I keep getting an Error "can't dup NilClass". That is, until I restart the server. Then I can list them just fine.
Debugging this issue, it turns out that the Error gets raised in ...
I just started reading the Objective-c tutorials, and there is a section on sending a message to nil.
What does this mean? I can't seem to follow it.
...
I have a form and I'm using jQuery to validate that the have entered in the correct information into the textboxs. That works fine, because I have this code:
var name = $("#business_name").val();
if (name == "") {
$('#namelabel').show()
$("#business_name").focus();
return false;
}
that tests to see if ...
I've learned that in dealloc you do [object release]; but in viewDidUnload (in a UIViewController subclass) you do self.object = nil. What is really the difference because self.object = nil (we're assuming object is a (nonatomic, retain) property) retains nil (which does nothing) and then releases the old value and then the reference cou...
So I thought I had all these questions all figured out. Then all of a sudden i get an error (a crash) i can't figure out. THen after doing research to remedy the crash, i notice everything that I thought i knew about these critical areas are somewhat wrong.
Below are 8 questions im just going to shoot out there in hopes of somebody answ...
What syntax do you think is better/more readable?
if(!myViewController.view.superview)
or:
if(myViewController.view.superview == nil)
Thanks!!
...
I am working on an iPhone app and am getting (null) references to IBOutlet fields in my controller. I have a UIViewController subclass that is set as the File's Owner in my XIB. I have a set of UI elements that are wired into the controller. After loading from NIB and attempting to set properties on those UI elements, I find that they ar...
Hey guys,
I have a general question about writing init methods in Objective-C.
I see it everywhere (Apple's code, books, open source code, etc.) that an init method should check if self = [super init] is not nil before continuing with initialisation.
The default Apple template for an init method is:
- (id) init
{
self = [super in...
When I get a memory warning I am releasing a bunch of objects stored in an NSMutableArray.
[_children release];
I also need to recurse through objects at some point (potentially after a mem warning has happened), so I need to check if the objects are still around, which I do with comparison to nil- which isn't going to work because re...
MyController *myViewController = [[MyController alloc] initWithNibName:@"myView" bundle:nil];
The nib file myView.nib has 2 uiimageviews and 2 uilabels. When I first init myViewController, all the 4 subviews are set as 0x0.
The second time I dont get such a behavior.
...
I am building a simple book check out application. One of the things that I need to do is determine if a book is checked out. I have my associations between my people and book classes setup through a book_check_out class. My goal is to use the checked_out property of book to determine if a book is presently checked out. However, in my pr...
At a point in my code, I expect current_part to sometimes be nil, and I want to run some code (inside an if block) when that's not the case.
Using script/server --debugger, I've established that current_part is in fact nil at that point when the following errors occur.
All the following versions generate the can't convert nil into Stri...
I set a property with this declaration:
@property (nonatomic,retain) NSDictionary *itemData;
to a dictionary with 1 key - val pair. The table view in my view then gets the one value for the dictionary fine as a section header. But when I go back to access that very same value, it is nil.
Any suggestions? I have been working on this f...
This is a sample code:
NSDictionary *myDictionary = [NSDictionary dictionary];
NSNumber *myNumber = [myDictionary valueForKey: @"MyNumber"];
NSLog(@"myNumber = %@", myNumber); // output myNumber = (null)
if (myNumber == nil)
NSLog(@"test 1 myNumber == nil");
if (myNumber == NULL)
NSLog(@"test 2 myNumber == NULL");
if ([myN...
I'm aware that it's perfectly fine to send messages to nil objects in Objective-C. However, I am curious if there is any runtime support for flagging such situations. I can see this being useful in testing/debugging situations.
...
Hi,
In a controller I have 2 actions
def action1
session[:test]="test"
render :text => session[:test] # output test
end
def action2
render :text => session[:test] # output nil
end
I perform first action1 so the session is set
Then I perform action2 but session[:test] is nil
So what am I doing wrong?
...