Objective-C function with default parameters?
Solution 1
There's no default parameters in ObjC.
You can create 2 methods though:
-(void)fooWithA:(int)a b:(int)b c:(int)c {
...
}
-(void)fooWithA:(int)a b:(int)b {
[self fooWithA:a b:b c:0];
}
For C : there's nothing special added to the C subset by using ObjC. Anything that cannot be done in pure C can't be done by compiling in ObjC either. That means, you can't have default parameters, nor overload a function. Create 2 functions instead.
Solution 2
No, objective-c does not support default parameters. See similar question
Solution 3
You can write a C function with a variable length argument list. You can use '...' as the data type for one of your function's declared parameters to specify where in the parameter list the variable argument list begins. (That allows you to have one or more required arguments before the start of the list.)
printf() is an example of a function that is written using this facility (known as varargs).
printf(const char *restrict format, ...);
Here, the first argument is required, and then can be followed by zero or more additional arguments.
If you wrote your function this way, it could supply a default value for the missing parameter.
Solution 4
For a C function - no. For an Objective C class method - yes, you just do two methods, one of them one parameter short, calling the other method.
Or you can rename your sources to .mm and C functions magically become C++.
Brian Postow
Updated on July 09, 2022Comments
-
Brian Postow almost 2 years
Possible Duplicates:
Optional arguments in Objective-C 2.0?
Objective-C Default Argument ValueI'm writing a C function in Objective-C. I want a default value for my last parameter.
I've tried:
foo(int a, int b, int c = 0);
but that's C++.
I've also tried:
foo(int a, int b, int c) { ... } foo(int a, int b) { foo(a, b, 0); }
But that's also C++.
Is there a way to do this in Objective-C instead?
-
palantus about 14 yearsDuplicate of stackoverflow.com/questions/871796/… and/or stackoverflow.com/questions/561185/…, I believe.
-
Brian Postow about 14 yearsThe first one was less helpful because everyone either answered for method call, or an incorrect statement that you can have two foo functions. The second is all method calls...
-
-
Brian Postow about 14 years@Kenny, yeah but this doesn't really belong to any class. it really is a stand alone C function...
-
Brian Postow about 14 yearsThat's an interesting possibility... I'll have to figure out the cost of that in other parts of my integration...
-
Macmade about 14 yearsThen as Seva sugest, try Objective-C++. With that, you will be able to mix C++ and Obj-C code, calling one from the other, etc... : )
-
Seva Alekseyev about 14 yearsNote that this changes global name decoration. You won't be able to call such a function externally from a .m/.c source; if there's a way to declare a function as "extern C++", so to say, I'm not familiar with it. In other words, if you're going ObjC++, you better do this throughout the project.
-
Necktwi about 7 yearsI have changed header file extension to
hh
, source file extension tomm
and In project settings it is setcompile source as according to file type extension
to compile it asobjective-C++
. but still it saysC does not support default arguments
. what is the correct extension forobjective-C++
header files? -
kennytm about 7 years@neckTwi
mm
. However, the error may happen if thehh
is included by non-ObjC++ files. -
Necktwi about 7 yearsI have a C++ function
NormalSmooth
declared in filenautical.hpp
and defined innautical.cpp
which I have renamed tonautical.hh
andnautical.mm
respectively. Now I am using the functionNormalSmooth
inGameViewController.m
. What should I do to avoid the above error? Thank you. -
kennytm about 7 years@neckTwi change GameViewController to
mm
as well. (Consider create a new question post) -
Necktwi about 7 yearsDone. Please look into stackoverflow.com/questions/43268483/… thank you
-
Motti Shneor about 5 yearsGod forbid!!! making it Objective-C++ you'll bare the curse of C++ forever. E.g. you cannot deploy your binary to others, because they'll need to compile their own code EXACTLY the same way you did. Same compiler, runtime-libs and settings. C++ has no standard/consistent ABI. The strongest reason OBJ-C is "pure C" - is to have a "compatible-forever" binary, that runs everywhere. You only use Obj-C++ when you need to interface C++ code from Obj-C. Certainly not to save a few simple-to-understand code-lines. If you're all for elegance - do Swift instead (and enjoy same perils as C++)