How to resolve property getter/setter method selector using runtime reflection in Objective-C? (or reverse)

Question

Objective-C offers runtime reflections feature. I'm trying to find getter/setter selector name of a declared property. I know the basic rule like field/setField:. Anyway I think runtime reflection should offer a feature to resolve the name for complete abstraction, but I couldn't find the function.

How can I resolve the getter/setter method selector (not implementation) of a declared property with runtime reflection in Objective-C (actually Apple's Cocoa)

Or reverse query. (method selector → declared property)

Answer 1

I think you can get the selector names only if the property is declared with explicit (setter = XXX and/or getter = XXX)

So to get the getter and setter selector names for some property 'furType' of the class 'Cat':

objc_property_t prop = class_getProperty([Cat class], "furType");

char *setterName = property_copyAttributeValue(prop, "S");
if (setterName == NULL) { /*Assume standard setter*/ }

char *getterName = property_copyAttributeValue(prop, "G");
if (getterName == NULL) { /*Assume standard getter */ }

I don't know of a reverse query, other than iterating through all the properties and looking for matches. Hope that helps.

Answer 2

A little update from my NSObject category. Hope this'll help some one:

+(SEL)getterForPropertyWithName:(NSString*)name {
    const char* propertyName = [name cStringUsingEncoding:NSASCIIStringEncoding];
    objc_property_t prop = class_getProperty(self, propertyName);

    const char *selectorName = property_copyAttributeValue(prop, "G");
    if (selectorName == NULL) {
        selectorName = [name cStringUsingEncoding:NSASCIIStringEncoding];
    }
    NSString* selectorString = [NSString stringWithCString:selectorName encoding:NSASCIIStringEncoding];
    return NSSelectorFromString(selectorString);
}

+(SEL)setterForPropertyWithName:(NSString*)name {
    const char* propertyName = [name cStringUsingEncoding:NSASCIIStringEncoding];
    objc_property_t prop = class_getProperty(self, propertyName);

    char *selectorName = property_copyAttributeValue(prop, "S");
    NSString* selectorString;
    if (selectorName == NULL) {
        char firstChar = (char)toupper(propertyName[0]);
        NSString* capitalLetter = [NSString stringWithFormat:@"%c", firstChar];
        NSString* reminder      = [NSString stringWithCString: propertyName+1
                                                     encoding: NSASCIIStringEncoding];
        selectorString = [@[@"set", capitalLetter, reminder, @":"] componentsJoinedByString:@""];
    } else {
        selectorString = [NSString stringWithCString:selectorName encoding:NSASCIIStringEncoding];
    }

    return NSSelectorFromString(selectorString);
}