Evaulate NSString and execute as Objective-C code

Question

This might be a completely ridiculous question, but is it possible to use a NSString as a substitute for a line of code?

for (int i = 0; i < 10: i++){    
    NSString *cam = @"locXCamProfileSwitch";
    ["%@", cam setOn:YES];
]

Also is it possible to concantinate the index i into the replacement of the X?

Answer 1

It's not generally possible (as far as I know), but it's possible to access ivars, properties, classes and methods by using strings.

• Instance variables and properties can be accessed like this:

  [self valueForKey:@"key"];
  

• Classes can be referenced like this:

  Class cls = NSClassFromString(@"MyClass");
  [cls aClassMethod];
  

• Methods can be used like this:

  SEL selector = NSSelectorFromString(@"myMethod:");
  [self performSelector:selector];
  

To replace a placeholder in a string with a number you can use a formatter:

NSString *cam = [NSString stringWithFormat:@"loc%dCamProfileSwitch", i];

That being said, it's never a good idea to have numbered variable names.

Use an array instead:

int switchCount = 10;
NSMutableArray *switches = [[NSMutableArray alloc] initWithCapacity:switchCount];
for (int i = 0; i < switchCount; i++) {
    CGRect rect = CGRectMake(10, 10+i*30, 70, 40); // or something like that.
    UISwitch *sw = [[UISwitch alloc] initWithFrame:rect];
    sw.tag = i;
    [sw addTarget:self action:@selector(switchChanged:) 
                 forControlEvents:UIControlEventValueChanged];
    [self.view addSubview:sw];
    [switches addObject:sw];
}
self.switches = [NSArray arrayWithArray:switches];  // assuming you have a property "switches".

Then you can simply iterate over it:

for (UISwitch *switch in self.switches) {
    [switch setOn:YES];
}

And be notified when one of them changes like this:

- (void)switchChanged:(id)sender {
    UISwitch *theSwitch = (UISwitch *)sender; // the switch that changed.
    int tag = theSwitch.tag;  // number of switch that changed.
    // do something....
}