if-let and guard macros for Objective C

iflet.m

#import <Foundation/Foundation.h>

// VARIABLE must be a variable declaration (NSString *foo)
// VALUE is what you are checking is not nil
// WHERE is an additional BOOL condition

#define iflet(VARIABLE, VALUE) \
    ifletwhere(VARIABLE, VALUE, YES)

#define ifletwhere(VARIABLE, VALUE, WHERE) \
    for (BOOL b_ = YES; b_ != NO;) \
        for (id obj_ = (VALUE); b_ != NO;) \
            for (VARIABLE = (obj_ ?: (VALUE)); b_ != NO; b_ = NO) \
                if (obj_ != nil && (WHERE))



// Called just like the swift verstion
// guard(1 < 2) else {
//     return
// }

#define guard(CONDITION) \
    if (CONDITION) {}

#define guardletwhere(VARIABLE, VALUE, WHERE) \
    ifletwhere(VARIABLE, VALUE, WHERE) {}



int main(int argc, char *argv[]) {
    @autoreleasepool {
        NSString *x = @"asdf";
        NSString *y = nil;
        
        iflet(NSString *z, x) {
            NSLog(@"x is not nil");
        }
        
        iflet(NSString *z, y) {
            NSLog(@"y is not nil");
        }
        else {
            NSLog(@"y is nil");
        }
        
        ifletwhere(NSString *z, x, z.length < 100) {
            NSLog(@"x is not nil and < 100");
        }
        
        guard(3 < 2) else {
            NSLog(@"guard failed");
        }
        
        guardletwhere(NSString *z, x, z.length < 3) else {
            NSLog(@"guardletwhere failed");
        }
    }
}

/* outputs:
 
 iflet[57328:5182484] x is not nil
 iflet[57328:5182484] y is nil
 iflet[57328:5182484] x is not nil and < 100
 iflet[57328:5182484] guard failed
 iflet[57328:5182484] guardletwhere failed
 
 */

suggesting change to

#define guardletwhere(VARIABLE, VALUE, WHERE) \
    VARIABLE = (VALUE); \
    if (VALUE != nil && (WHERE)) {}

1. to support continue in if let's else
2. to keep VARIABLE in the code, same behavior with Swift

There is an issue when calling 'continue' in these macros, as they are in for loop without brackets

What difference would it make if they were in a loop with brackets? I see no difference in behavior.

suggesting change to

Yet this approach has two other drawbacks:

1. VARIABLE will be available outside of the iflet block, which does not match if let behavior in Swift. Also you cannot use the same variable for two iflet blocks in a row as the compiler will throw a re-declaration error but this is also possible in Swift.
2. You cannot use iflet as an else statement (else iflet (...)) or after another if (if (...) iflet(...)). Both will not create a compile error but the code won't do what you expect it to do.