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Editorial Team
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Asked: 2026-05-24T03:52:47+00:00

this is really a newbie question, but it would help me to have a

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this is really a newbie question, but it would help me to have a better understanding of how Objective-c works. I have made use of UIActionSheet in a iOS app. Looking at documentation this is the relevant init method:

- (id)initWithTitle:(NSString *)title delegate:(id < UIActionSheetDelegate >)delegate cancelButtonTitle:(NSString *)cancelButtonTitle destructiveButtonTitle:(NSString *)destructiveButtonTitle otherButtonTitles:(NSString *)otherButtonTitles, ...

Where otherButtonTitles is said to be a comma separated list of NSString. In my mind this is correspondent to an NSArray, so with the intent of caushing a crash I tried:

NSArray *buttons = [NSArray arrayWithObjects:@"B1",@"B2",nil];
UIActionSheet *sheet = [[UIActionSheet alloc] initWithTitle:@"Actions" delegate:self cancelButtonTitle:@"Cancel" destructiveButtonTitle:@"Delete" otherButtonTitles:buttons];

And then obviously the application crashed because of buttons NSArray.
This sounds so similiar to Java varargs, where in a class you can have something like:

public void myMethod(String... param) {...};

A legal call to this method is:

myClass.myMethod("x");
myClass.myMethod("x","Y");

I have a lot of methods in my iOS apps that made use of NSArray:

[myClass myMethod:[NSArray arrayWithObjects:....]];

And it would be very convenient for me to avoid alloc of NSArray but rather passing a comma separated list of NSString. How can I do that ? I mean, from the myMethod point of view, what type of param is received and how should it be considered ? For example how can I cycle trough an NSString ???

thanks

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1 Answer

  1. Editorial Team

    As the king of Objective-c newbie as I am, here comes a little misundertanding for me. As pointed out by Graham, the method made indeed use of variable arguments. At first glance I completely missing this, the Java varargs notation has this equivalent in Objective-c: 

    public void myMethod(String... var);
-(void)myMethod:(NSString*)var,...;

    Infact if you take a look at UIActionSheet method signature it put exactly the same three dot notation in the part regarding other buttons:

    otherButtonTitles:(NSString *)otherButtonTitles, ...

    Also for dealing with variable arguments in objective-c I found a very useful link:

    http://cocoawithlove.com/2009/05/variable-argument-lists-in-cocoa.html

    Coming to my question, I can safely rewrite all my methods by implementing the ‘three dot notation’, and throw away all the unnecessary NSArray.

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