Objective C - Using insertString for an NSMutable string

Question

With a NSMutableString, how would I insert a "-" sign at the index "0" for an NSMutableString called "a". Right now my code looks like this:

a = [insertString: @"-" atIndex: 0];

Xcode throws an error saying that 'insertString' is undeclared. Something looks very wrong with my code. Please give me guidance.

Answer 1

put the object inside the brackets:

[a insertString: @"-" atIndex: 0];