How to convert a number to its enum?

Question

I've declared an enum like so:

typedef enum
{
    firstView = 1,
    secondView,
    thirdView,
    fourthView
}myViews

My goal is that a UIButton will trigger another function with the uiButton sender.tagand that function will know to convert the integer to the correct view. I'm aware that I can just create an array with the names of the views but I am looking for something smarter than that using the declared enum.

Example:

-(void)function:(UIButton *)sender
{
  ...
  ...
  NSLog(@"current View: %@",**converted view name from sender.tag);
}

Thanks

Sulthan · Accepted Answer · 2013-05-26T15:37:18.713

3

Well, the best solution is to actually store the views. You can also use a IBOutletCollection to create the array. Declaring an enum is just another way to store names.

self.views = @[firstView, secondView, thirdView, forthView];

...

button.tag = [self.views indexOfObject:firstView];

...

- (void)buttonTappedEvent:(UIButton*)sender {
    UIView* view = [self.views objectAtIndex:sender.tag];
}

PS: converting tag into enum is trivial, it's just myViews viewName = sender.tag, possibly with a cast myViews viewName = (myViews) sender.tag

edited May 26 '13 at 15:37

answered May 26 '13 at 15:31

Sulthan

128,090
22
218
270

I just saw that you gave the same solution I ended up doing. One question, `myViews viewName = (myViews) sender.tag; NSLog(@"View #: %u",viewName);` will output a number and not the enum name – Segev May 27 '13 at 07:12
@EXEC_BAD_ACCESS True. An enum is just a symbolic name. If you write `int a = 1; NSLog(@"%d", a)`, you don't expect it to output `a`. If you want to log a descriptive name, you have to convert the enum value to a string. There are different ways how to do it - e.g. declaring a second array with names or X-macros. In most situations the integer number is enough because you know what it means. – Sulthan May 27 '13 at 09:23

score 0 · Answer 2 · answered May 26 '13 at 13:55

0

How about storing it inside a NSMutableDictionary ?

NSMutableDictionary *viewList = [[NSMutableDictionary alloc] init];

for(int i = 1; i <= 4; i++)
{
    [viewList setObject:@"firstView" forKey:[NSString stringWithFormat:@"%d", i]];
}

...

-(void)buttonTappedEvent:(id)sender
{
    UIButton *tappedButton = (UIButton *)sender;

    NSLog(@"current view: %@", [viewList objectForKey:[NSString stringWithFormat:"%d", tappedButton.tag]]);
}

answered May 26 '13 at 13:55

Zhang

11,549
7
57
87

"I'm aware that I can just create an array with the names of the views but I am looking for something smarter than that using the declared enum." – Segev May 26 '13 at 13:56
Enums are only for ordinal types apparently: http://stackoverflow.com/questions/1851567/chow-to-use-enum-for-storing-string-constants. What is your ultimate goal, what are you trying to achieve with views and enums? Dynamically load views in certain orders on the iPhone screen ? – Zhang May 26 '13 at 13:58
It's a bit more complex than that. Looks like an array is my only option. – Segev May 26 '13 at 14:08

andykkt · Answer 3 · 2013-05-26T14:34:30.810

What I normally do is declare it to dictionary for once using dispatch once

static NSDictionary* viewList = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
        viewList = [NSDictionary alloc] initWithObjectsAndKeys:[NSNumber numberWithInt:1], @"firstView",[NSNumber numberWithInt:2], @"secondView",[NSNumber numberWithInt:2], @"thirdView",@"secondView",[NSNumber numberWithInt:3], @"fourthView",
nil];
    });

and find with tag like this:

-(void)function:(UIButton *)sender
{
  NSLog(@"current View: %@",[viewList objectForKey:[NSNumber numberWithInt:sender.tag]);
}

How to convert a number to its enum?

3 Answers3