Switch with typedef enum type from string

I'm trying to get a value from a string that belongs to an enum typedef in Obj C but I don't seem capable of geting the value out of the NSString. I'me doing something like this:

typedef enum{
    S,
    M,
    L
} Size;

-(void)function:(NSString *)var{
Size value=[var value];
swicth(value)开发者_JAVA技巧{
  case S:...
  case M:...
  ...
 }
}

EDIT: The contents of the string would br something like @"S" @"M" @"L"

I don't see how can I accomplish this.

Assuming that you know that the strings are of length one, you can switch on the unichar at position 0.

switch ([string characterAtIndex:0]) {
case 'S': ...
case 'L': ...
case 'M': ...
}

It's not clear what the string contains. Is it @"S", @"M" or @"L"? If so, you need to provide your own conversion to the values of the Size enumeration. Or you could just use string comparison in your method:

if ([var isEqualToString: @"S"]) {
  // ...
} else if ([var isEqualToString: @"M"]) {
  //...
} ...

However, if the string contains the numeric value of one of the Size entries (like @"0", @"1" or @"2") you can use the -intValue method to do the comparison you wrote in the question.