I import oourafft.h and oourafft.m class, but get strange error while ooura initialize.
OouraFFT * myFFT = [OouraFFT initForSignalsOfLength:1024 numberOfWindows:10];
OouraFFT may not respond to +initForSignalsOfLength: numberOfWindows
Messages without matching method signature will be assumed to return 'id' and accept argument - Warning
I think that it some kind of error import .h file
You are trying to call class method which does not exist in OouraFFT - this method is instance method, so you need to allocate object at first.
You should do the following:
OouraFFT * myFFT = [[OouraFFT alloc] initForSignalsOfLength:1024 andNumWindows:10];
And don't forget that you own object after this, therefore you should release or autorelease in an appropriate place.
Related
I must be missing something simple here. Anyway, I started out by just making a regular function,
NSDecimalNumber* aa(NSMutableString *string)
{code}
which I would then call by pressing a button like so:
- (IBAction)parse:(id)sender {
string1=[NSMutableString stringWithFormat:#"%#", screen.text];
NSDecimalNumber *output=aa(string1);}
(screen.text is from a label) However, partway into it, I realized that the function can't use variables from the rest of my viewcontroller.m class (and vice-versa), so I decided to implement the function as a method instead. Here's what I did. First, I added this to viewcontroller.h,
+ (NSDecimalNumber*) aa:(NSMutableString*) string;
#property (nonatomic, strong) NSDecimalNumber *number; //the number I'm working with
synthesized my property, changed my function declaration to this,
+ (NSDecimalNumber*) aa:(NSMutableString*) string
and attempted to call it like this,
NSDecimalNumber *output=[[NSDecimalNumber alloc] aa:string1];
With that attempt, I got two errors -- "No visible #interface for 'NSDecimalNumber' declares the selector 'aa,'" and "instance variable 'number' accessed in class method."
So I tried again with an instance method. Changed the +'s to -'s and instead called the method with
NSDecimalNumber *output;
[output aa:string1];
That corrected the second error but not the first one. I can't figure out why it isn't recognizing the method in the #interface. Also, those weren't the only things I've tried changing -- I've been playing around with multiple ways to call the method, but nothing seems to work. Any ideas?
This function call:
NSDecimalNumber *output=[[NSDecimalNumber alloc] aa:string1];
..is attempting to call aa an instance of NSDecimalNumber. I don't think that's what you want, isn't your aa method a member of your class? Also, you're not calling a class initializer (although you don't need to, since your method is static so long as its definition starts with +):
// MyClass method definition
+ (NSDecimalNumber*) aa:(NSMutableString*) string
// Called with
NSDecimalNumber *output=[MyClass aa:string1];
--UPDATE--
To address the "instance variable" error, you need to make the method an instance method. Change + in definition to - and call it thusly:
// MyClass method definition
- (NSDecimalNumber*) aa:(NSMutableString*) string
// Call it like this _if calling from within MyClass only_ (hence, "self")
NSDecimalNumber *output = [self aa:string];
If you want to add methods to NSDecimalNumber, you need to use a category. Your code adds a method to your view controller subclass.
I am using XCode 4.0.2 for a iOS4 project.
I have this class method that construct an object. This is a constant that i need occasionally from start to end of the app.
However, running the Analyze tool this gives me a "Potential leak of an object" warning for the c object.
Should I be concerned? How can I fix it?
Thank you
You should read the Memory Management Programming Guide provided by Apple.
You should prefix your method name (+[XYZ A] in this instance) with new to make it clear that callers of your method know that they are responsible for releasing the object they receive. You would rename the method to +[XYZ newA].
If you do not wish to rename your method, you should at least return an autoreleased object, e.g. change the last line to return [c autorelease];
Every time you use that method, it creates a new instance of XYZ through the (deprecated) +new method.
If you want a single object of class XYZ that persists to the end of the app, you'll need to make some changes. The simplest way is to create this object on class initialization. In the .m file for whatever class we're looking at here, add the following:
static XYZ *instance = nil;
+ (void)initialize {
if (self != [ThisClass class])
return;
instance = [[XYZ alloc] init];
instance.X = ...;
instance.Y = ...;
instance.Z = ...;
}
And then, your A method:
+ (XYZ *)A {
return instance;
}
This is the code
Dest.h
#import <UIKit/UIKit.h>
#import <CoreGraphics/CGPDFArray.h>
#class Model;
// snip
#interface Dest : NSObject
{
CGPDFArrayRef destArray;
DestKind kind;
}
+ (id)destWithObject:(CGPDFObjectRef)obj inModel:(Model*)model;
- (id)initWithArray:(CGPDFArrayRef)array;
Dest.m
#implementation Dest
+ (id)destWithObject:(CGPDFObjectRef)obj inModel:(PDFModel*)model
{
CGPDFArrayRef array = NULL;
Dest* dest = nil;
// stuff to create array
if (array)
{
dest = [[[Dest alloc] initWithArray:array] autorelease];
<path>/Dest.m:63: warning: passing argument 1 of 'initWithArray:' from incompatible pointer type
}
return dest;
}
Clearly the compiler thinks that array is incompatible with initWithArray: declared in Dest.h. But as far as I can see, the type is exactly right. I even copied the declaration from Dest.h and pasted it in Dest.m. initWithArray: compiles fine. Adding/removing the CGPDFArray.h header file in Dest.h doesn't make any difference, the compiler doesn't think it is an int in Dest.h.
I have a feeling you're leaving out another warning that's relevant — "warning: multiple methods named 'initWithArray:' found". If I'm right, this is what you're running into:
There are two method signatures that go with that selector. NSArray's takes an NSArray* and yours takes a CGPDFArrayRef.
alloc returns id. This means that the compiler has no idea what class it returns (yes, the compiler is that thick).
You then send initWithArray: to this mystery object. The compiler says, "Gosh, I don't know what kind of object this is, so I can't decide which method signature is correct. I'll spin around really fast and whichever one I'm facing is the one I'll pick." It chooses NSArray's signature. Then it looks at the argument and says, "Hey, that's not an NSArray! Error!"
The quick-and-easy solution is to change it to [[(Dest*)[Dest alloc] initWithArray:array] autorelease]. The better solution is to choose a distinct selector for your method.
Oh don't do that. Only CFArrayRefs are 'toll-free bridged' to NSArray. The CGPDFArrayRef however is completely different and incompatible. You can not use those as NSArrays.
The PDF API sure looks like a standard Core Foundation compatible one, but it really is not.
From Apple's documentation,
CGPDFArray header file defines an
opaque type that encapsulates a PDF
array
so it cannot be used as a NSArray.
This is an objective-c question.
I would like to call a method in an object, but there is no instantiation of the object. Is this possible?
The method I want to call is not a class method.
You can't call a method on an object that doesn't exist. But you can call a method on a class even if you have no instantiated objects of that class. (That's what alloc is in #fbrereton's answer -- a class method).
Class methods are declared and defined with a + instead of a -, are called on the class rather than the instance, and cannot access self or any instance variables in the class (for reasons that should be obvious).
Unless the method is static you will not be able to do this. static routines in Objective-C will be prepended with a +. For example NSObject provides these two routines (among many):
+ (id)alloc; // static - an NSObject instance is not required
- (NSString*)description; // nonstatic - an NSObject instance is required
One would make the respective calls like so:
NSObject* result = [NSObject alloc];
NSString* desc = [result description];
Sorry to nit-pick Chris' terminology, but we don't call a method on an object in Objective-C, we send a message to an object. When you send a message, the runtime will look up the appropriate method and call it. The distinction matters.
Perhaps you just want a plain-old C function. If you don't want a class method, and you don't want an instance method, that appears to be your only option. Don't be afraid of using C functions in Objective-C. Every technique has its place.
You can indeed invoke an instance method without an instance, provided it is functionally a class method (that is, it accesses no instance variables). Here's an example:
/*
Compile with:
gcc -framework Foundation inst_method_without_inst.m -o inst_method_without_inst
*/
#import <Foundation/Foundation.h>
#import <objc/runtime.h>
#interface Foo : NSObject {
}
- (BOOL)doSomethingWithThis:(NSString *)this;
#end
#implementation Foo
- (BOOL)doSomethingWithThis:(NSString *)this {
NSLog(#"Look, it's this: %#", this);
return YES;
}
#end
typedef BOOL (*my_sel_t)(id, SEL, NSString *);
int
main(void) {
Class cls = [Foo class];
SEL my_sel = #selector(doSomethingWithThis:);
Method m = class_getInstanceMethod(cls, my_sel);
// You could also use +[NSObject instanceMethodForSelector:] to get |m|,
// since |cls| is a kind of NSObject.
my_sel_t f = (my_sel_t)method_getImplementation(m);
BOOL result = f(nil, my_sel, #"Hello from an instanceless instance method invocation!");
NSLog(#"result: %d", (int)result);
return EXIT_SUCCESS;
}
You could get it to work even if the instance method accesses instance variables by allocating memory for it to work with (using either +alloc or class_getInstanceSize() plus malloc()) and passing a pointer to that memory as the first id argument to the implementation instead of nil.
While this is entertaining as an exercise, I can't think of a good reason to not just instantiate the class and use the standard messaging syntax and compiler support. In fact, the only reason we couldn't just do [(Foo *)nil doSomethingWithThis:#"BOO!"] here is that objc_msgSend() special-cases messages to nil with the result that NO is returned and nothing happens.
I have defined a constants class within my iphone program using the 'extern' and 'const' keywords as in the example described in:
Constants in Objective-C
At this point, I am trying to initialize some string constants from the contents of a plist file, instead of being defined right in the class, e.g., instead of having:
// Constants.m
NSString * const MyConstant = #"a constant";
I would like to have it initialized somewhere from the plist file. So far, I have done a test using the static +(void)load method, but I am not completely happy about it, e.g.:
// Constants.m
NSString * ALERT_QUIT_TITLE;
#implementation Constants
+ (void)load {
// this controller contains all the strings retrieved from the plist file
LabelsController *labels = [LabelsController instance];
ALERT_QUIT_TITLE = labels.alertQuitTitle;
}
#end
Using a log call I can verify that the load code gets called early in the app startup, even before the AppDelegate constructor. However, two things I see not good in this approach:
I have to remove the 'const' keyword, otherwise I get a compile error since I am trying to initialize a variable that is defined as constant
I get some sort of warning message about the autoreleased pool:
*** _NSAutoreleaseNoPool(): Object 0x50b330 of class NSPathStore2 autoreleased with no pool in place - just leaking
Stack: (0x905caf0f 0x904d8647 0x904e039f (etc)
I guess I could use a direct call to the Labels controller to retrieve the label, but I would like more to treat it like a constant having all the maint. advantages it provides.
Which would be the correct (recommended) way to initialize a constant from an external source, like in this case a plist? Hope you can help, I have lost a good few hours trying to resolve this!
Thank you in advance.
If you initialize from a plist file, then you do not have a constant. And you should not define it as such.
I am guessing what you want is to be able to treat this value as if it was a constant? And that can be achieved using lazy initialization instead.
NSString* AlertQuitTitle()
{
static NSString* title = nil;
if (title == nil)
{
LabelsController* labels = [LabelsController instance];
title = labels.alertQuitTitle;
}
return title;
}
Is there a good reason as to why you do not use the NSLocalizedString() macro to fetch the alert quit title?
The warning
As the warning states, you are executing the +load method outside of an auto release pool. Meaning that all calls to autorelease just leak memory. You can fix your method like this:
+ (void)load
{
// this controller contains all the strings retrieved from the plist file
NSAutoreleasePool* pool = [NSAutoreleasePool new];
LabelsController *labels = [LabelsController instance];
ALERT_QUIT_TITLE = labels.alertQuitTitle;
[pool release];
}
I would suggest using the NSUserDefaults method instead for storing data.
Load is called far too early in the process for most purposes. Even initialize is fairly early. As you've noted, there is no autorelease pool setup, so any use of it (which is quite hard to avoid) will give you warnings and possible leaks.
A better way to do it is to forget the constant entirely, and write LabelController alertQuitTitle to lazily initialize its database and cache its answer. Something like this (untested, uncompiled).
+ (NSDictionary*) labelStrings;
{
static NSDictionary* strings = nil;
if ( !strings ) {
// Allocate and laod and keep ownership of the NSDictionary
}
return strings;
}
+ (NSString*) alertQuitTitle
{
static NSString* alertQuitTitle = nil;
if ( !alertQuitTitle ) {
alertQuitTitle = [[LabelController strings] objectForKey:#"alertQuitTitle"];
}
return alertQuitTitle;
}
If you really want, you can convert alertQuitTitle into a macro and use that to easily create dozens of methods.
In your other code, if you really want to, you can write a method that caches the answer as well, but thats fairly pointless, instead just use [LabelController alertQuitTitle].
You can, if you prefer, use a singleton, but there is not much point even creating a single instance of LabelController unless you have other things for it to do - any data it needs can be stored as static variables. A singleton would be more inline with typical Cocoa behaviour though. Either way, the same technique will work.
To directly answer your question, it looks like you're calling load before an NSAutoreleasePool has been set up. Every thread needs its own NSAutoreleasePool; your main thread's NSAutoreleasePool is set up in main.m, which you can see if you open up that source file.
I usually initialize my application's globals in my App Delegate's init method.
But this looks like unnecessary optimization, and it's creating problems as a result. You should consider using string resources for something like this. See NSBundle localizedStringForKey:value:table:, and NSLocalizedString()