Clarification on self in Objective-C

self refers to an instance of the class in instance methods, or the class itself in class methods.

if I had an instance method and inside that method I had something like

    //calls runSomeMethod on whatever instance of the class is calling it. self in this case refers to an instance of the class
    [self runSomeMethod]

if I had a class method (take initialize for instance)

+ (void)initialize {
    //self refers to the current class. so if this was in THDanceNode then self = THDanceNode
    if (self == [THDanceNode class]) { 
        // ...
    }
}

so back to your original question:

then [self runAction:repeatAction] is essentially equal to [THDanceNode runAction:repeatAction].

the above is true if self was used inside a class method. if its not inside a class method then that is not correct. self refers to an instance of the class, or the actual object of the class itself thats calling the method when not in a class method. since spriteKit actions are run on objects, its more likely that the above is used inside an instance method and that self refers to an instance of THDanceNode, not the class THDanceNode, but I cant be sure without seeing some more code.