Does iPhone SDK Objective C support functions inside of functions? - objective-c

Question

I know that javascript, for example supports functions inside of functions, like so:
function doSomething(){
function doAnothingThing(){
//this function is redefined every time doSomething() is called and only exists inside doSomething()
}
//you can also stick it inside of conditions
if(yes){
function doSomethingElse(){
//this function only exists if yes is true
}
}
}
Does objective-c support this? Theoretical example:
-(void) doSomething:(id) sender{
-(void) respondToEvent: (id) sender{
//theoretically? ... please?
}
}
BONUS: What is the proper term for a "local" function?

Answer 1

A bit late, but you can place an inline block into a function, which kind of acts like your nested function questions.
-(int)addNumbers:(int)a withB:(int)b withC:(int)c {
// inline block
int(^inlineaddNumbers)(int, int) = ^(int a, int b) {
return a + b;
};
if( a == 0 ) return inlineaddNumbers(b,c);
else return inlineaddNumbers(a,c);
}
It's a bit messy, but it works!

Answer 2

The usual term is nested function. gcc supports nested functions as an extension to C (disabled by default). I don't think this option is available with Objective-C (or C++) with gcc though, and even if it were it's probably not a good idea to use it (portability etc).
gcc.gnu.org/onlinedocs/gcc/Nested-Functions.html

Answer 3

By default Xcode disallows nested functions.
If you want to switch them on, open up the Info for your project, go to the Build tab, and set "Other C flags" (under the section titled "GCC 4.2 - Language") to "-fnested-functions".
(This is stored in your project.pbxproj file as "OTHER_CFLAGS = "-fnested-functions";"

Answer 4

Expanding the answer provided by Gui13 a little bit, with object parameters.
The following code snippet demonstrates how to draw an 11x5 set of UILabels.
// inline block - to be called as a private function
UILabel *(^createLabel)(CGRect, NSString *, UIColor *) = ^UILabel *(CGRect rect, NSString *txt, UIColor *color) {
UILabel *lbl = [UILabel new];
lbl.frame = rect;
lbl.textColor = color;
lbl.backgroundColor = [UIColor whiteColor];
lbl.font = [UIFont systemFontOfSize:30.f];
lbl.textAlignment = NSTextAlignmentCenter;
lbl.text = txt;
return lbl;
};
// loop to create 11 rows of 5 columns over the whole screen
float w = CGRectGetWidth([UIScreen mainScreen].bounds);
float h = CGRectGetHeight([UIScreen mainScreen].bounds);
float top = h / 10; //start at 10% from top
float vOffset = h / 13; //space between rows: 7.6% of screen height
NSArray *xFrom, *xTo; //columns to start at 5%, 20%, 40%, 60%, 80%
xFrom = #[#(1.f/20), #(1.f/5), #(2.f/5), #(3.f/5), #(4.f/5)];
xTo = #[#(1.f/5-1.f/16), #(2.f/5-1.f/16), #(3.f/5-1.f/16), #(4.f/5-1.f/16), #(19.f/20)];
#define SFMT(format...) [NSString stringWithFormat:format]
for (int row=0; row<11; row++) {
for (int col=0; col<5; col++) {
CGRect rect = CGRectMake([xFrom[col] floatValue]*w, top+row*vOffset, [xTo[col] floatValue]*w-[xFrom[col] floatValue]*w, vOffset*0.9);
UILabel *lbl = createLabel(rect, SFMT(#"%i-%i", row, col), [UIColor blueColor]);
[<my-view> addSubview:lbl];
}
}
Here is the output for this code:

Answer 5

#Moshe You cannot actually provide the nested functions inside the Objective C. Instead you can use the feature in latest Swift 3 which enables this feature. It will be like below:
func someFunction(input:String)->String
{
var inputString = input;
func complexFunctionOnString()
{
inputString = "Hello" + input;
}
complexFunctionOnString();
return inputString;
}
someFunction("User");