A Note to Objective-C Developers

WebScript uses a subset of Objective-C syntax, but its role within an application is significantly different. The following table summarizes some of the differences.

Objective-C  				WebScript
_____________________________________________________________________________

Is compiled  				Is interpreted

Supports primitive C data types    	Only supports the id data type

Requires method prototyping  		Doesn't require method prototyping
 					(that is, you don't declare methods 
					before you use them)

Usually includes a .h and a .m file  	Usually has corresponding declarations
 					and HTML template files (unless it is
					an application script)

Supports all C language features  	Has limited support for C language 
					features; for example, doesn't support 
					structures, pointers, enumerators, or 
					unions
					
Methods not declared to return void   	Methods aren't required to include a
must include a return statement  	return statement
 
Has pre-processor support  		Has no pre-processor support---that is,
 					doesn't support the #import or #include
					statements  
_____________________________________________________________________________

Perhaps the most significant difference between Objective-C and WebScript is that in WebScript, the only valid data type is id. Some of the less obvious implications of this are:

You can't use methods that take non-object arguments (unless those arguments are integers or floats, which WebScript converts to NSNumbers). For example, in WebScript the following statement is invalid:
```
// NO!! This won't work.  
string = [NSString stringWithCString:"my string"];
```

You can only use the "at sign" character (@) as a conversion character with methods that take a format string as an argument:

// This is fine.
[self logWithFormat:@"The value is %@", myVar];
    
// NO!! This won't work.
[self logWithFormat:@"The values are %d and %s", var1, var2];

You shouldn't supply any type information for a method's arguments and return types. These types are assumed to be id, and if you supply any type information, you will get an error.
```
// This is fine.
- aMethod:anArg {
	    
// NO!! This won't work.
- (void) aMethod:(NSString *)anArg {
	    
// This won't work either
- (id)aMethod:(id)anArg {
```
You need to substitute integer values for enumerated types.
For example, suppose you want to compare two numeric values using the enumerated type NSComparisonResult. This is how you might do it in Objective-C:
```
result = [num1 compare:num2];  
if(result == NSOrderedAscending)   /* This won't work in WebScript */
    /* num1 is less than num2 */
```
But this won't work in WebScript. Instead, you have to use the integer value of NSOrderedAscending, as follows:
```
result = [num1 compare:num2];  
if(result == -1)  
    /* num1 is less than num2 */
```