Sprite kit, how can i randomly call a method? - iphone

Question

I am programming my game at the moment in sprite kit, I have 8 differnt methods and i have it set up to call a 1 method every 5 seconds, but instead of just being able to call 1 method i want it to randomly select 1 of the 8 methods and call that. Here is my current code:
- (void)updateWithTimeSinceLastUpdate:(CFTimeInterval)timeSinceLast {
self.lastSpawnTimeInterval += timeSinceLast;
if (self.lastSpawnTimeInterval > 5) {
self.lastSpawnTimeInterval = 0;
[self shootPizza];
}
}
- (void)update:(NSTimeInterval)currentTime {
// Handle time delta.
// If we drop below 60fps, we still want everything to move the same distance.
CFTimeInterval timeSinceLast = currentTime - self.lastUpdateTimeInterval;
self.lastUpdateTimeInterval = currentTime;
if (timeSinceLast > 1) { // more than a second since last update
timeSinceLast = 1.0 / 60.0;
self.lastUpdateTimeInterval = currentTime;
}
[self updateWithTimeSinceLastUpdate:timeSinceLast];
}

Answer 1

You could use selectors to achieve your goal.
Eg.
- (IBAction)performRandomMethod:(id)sender {
// put the method names as NSStrings into an array
// selectors are not objects, thus we convert to NSValue to allow storage in NSArray
NSArray *applicableMethods = #[[NSValue valueWithPointer:#selector(doA)],
[NSValue valueWithPointer:#selector(doB)],
[NSValue valueWithPointer:#selector(doC)]];
// randomly pick one of the objects from the array and convert back to a selector
NSUInteger randomIndex = arc4random_uniform(applicableMethods.count);
SEL randomMethodSelector = [[applicableMethods objectAtIndex:randomIndex] pointerValue];
// perform the selector
// ARC may complain regarding a selector leak - we can suppress with the following pragma marks
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
[self performSelector:randomMethodSelector withObject:nil];
#pragma clang diagnostic pop
}
- (void)doA {
NSLog(#"doA");
}
- (void)doB {
NSLog(#"doB");
}
- (void)doC {
NSLog(#"doC");
}
For more information on the code to suppress the selector leak warning, you should refer to the following question: performSelector may cause a leak because its selector is unknown
An intro to selectors can be found in Cocoa Core Competencies: Selector (Apple Docs)

Answer 2

This generates a random number between 0 and 7 inclusive.
#include <stdlib.h>
...
...
int method = arc4random() % 8;
You can then use integer stored in method to select between your various methods.