Modify Object while Iterating over a NSMutableArray

Question

I was trying to modify an object from an array while iterating over it and couldn't find a nice way of doing it... This is what I've done, is there a simpler way of doing this? I've been googling for while but I couldn't find anything...

NSMutableArray *tempArray = [[NSMutableArray alloc]init];
NSArray *days = [restaurant.hours componentsSeparatedByString:@","];
for (NSString *day in days) {
      NSString *dayWithOutSpace = [day stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]];
      [tempArray addObject:dayWithOutSpace];
}
days = [NSArray arrayWithArray:tempArray];

Thanks!

CRD · Accepted Answer · 2017-05-25 17:24:27Z

2

As suggested by others there might be better ways to accomplish the exact task in the question, but as a general pattern there is nothing wrong with your approach - build a new array.

However if you need to modify a mutable array, say because multiple objects reference it, there is nothing wrong with that either - that is why it is mutable after all! You just need to use standard iteration rather than enumeration - the latter is just the wrong tool for the job. E.g.:

NSMutableArray *anArray = ...

NSUInteger itemCount = [anArray count];
for(NSUInteger ix = 0; ix < itemCount; ix++)
{
   // read from anArray[ix] and store into anArray[ix] as required
}

edited May 25, 2017 at 17:24

answered Mar 17, 2014 at 17:51

CRD

53k5 gold badges73 silver badges87 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Odrakir · Accepted Answer · 2014-03-17 15:58:26Z

1

The way you do it is OK, since you are not modifying the array you are looping through.

Here is another way, a little less intuitive and probably not faster:

NSArray* days = [[[restaurant.hours componentsSeparatedByString:@" "] componentsJoinedByString:@""] componentsSeparatedByString:@","];

answered Mar 17, 2014 at 15:58

Odrakir

4,2341 gold badge24 silver badges52 bronze badges

Comments

Anindya Sengupta · Accepted Answer · 2014-03-17 15:51:33Z

0

Considering your hours string is like: 2, 5, 6, 7 etc. you can use the string as @", " directly.

NSArray *days = [restaurant.hours componentsSeparatedByString:@", "];

answered Mar 17, 2014 at 15:51

Anindya Sengupta

2,5992 gold badges21 silver badges27 bronze badges

2 Comments

Andres Over a year ago

it's an example, suppose you have to do something more than removing a leading space.

Anindya Sengupta Over a year ago

Don't really understand what you are looking for. Are you asking for better ways to access the objects in the array?

malex · Accepted Answer · 2014-03-17 15:59:29Z

0

Maybe it is better to eliminate all white spaces before separation.

NSString *daysWithOutSpaces = [restaurant.hours stringByReplacingOccurrencesOfString:@"[\\s\\n]" withString:@"" options:NSRegularExpressionSearch range:NSMakeRange(0, restaurant.hours.length)];
NSArray *days = [daysWithOutSpaces componentsSeparatedByString:@","];

answered Mar 17, 2014 at 15:59

malex

10.1k4 gold badges60 silver badges81 bronze badges

Collectives™ on Stack Overflow

Modify Object while Iterating over a NSMutableArray

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

4 Answers 4

Comments

Comments

2 Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related