Objective-C方法重载

Question

I am having doubt in Objective-C Method Overloading. Java supports method overloading with the same name , same number of arguments of different types . But when I try to do similar declaration in Objective-C, it throws me the error Duplicate declaration of method . Consider the following code,

/* Java */

int add(int i, int j);
int add(int i, int j, int k); // Accepted
float add(float i, float j); // Accepted

/* Objective-C */

- (int)add:(int)i and:(int)j;
- (int)add:(int)i and:(int)j and:(int)k; // Accepted
- (float)add:(float)i and:(float)j; // Throws error

Why is this not supported in Objective-C? Is there an alternative for this?

Answer 1

It simply isn't supported in Objective-C. It wasn't supported in plain old C, so it isn't all that surprising that Objective-C likewise did not add method overloading. For clarity, this can sometimes be good. Typically, the way around this is to include some information about the parameter in the function name. Ex:

- (int) addInt:(int)i toInt:(int)j;
- (int) addInt:(int)i toInt:(int)j andInt:(int)k;
- (float) addFloat:(float)i toFloat:(float)j;

Answer 2

Starting with this:

- (int)add:(int)i and:(int)j;

This does not override anything -- it is just another method:

- (int)add:(int)i and:(int)j and:(int)k; // Accepted

The following isn't accepted specifically because Objective-C does not allow for co-variant or contra-variant method declarations. Nor does Objective-C do type based dispatch overloading a la Java and C++.

- (float)add:(float)i and:(float)j; // Throws error

Note that Java was derived quite directly from Objective-C.