Is it possible to use a wildcard in KVC? - objective-c

Question

I'm trying to use wildcard in KVC like this.
Is it possible?
Or Is there other ways to use a wildcard to indicate a member variable?
#interface MyClass : NSObject
#property(nonatomic, retain) NSNumber *test1;
#property(nonatomic, retain) NSNumber *test2;
#end
#implementation MyClass{
NSNumber * test1;
NSNumber * test2;
}
#synthesize test1;
#synthesize test2;
#end
using wildcard
MyClass *testClass = [[[MyClass alloc] init] autorelease];
testClass.test1 = #50;
NSLog(#"test value : %#", [testClass valueForKey:#"*1"]);
For detail codes.
A real reason i wanted is to indicate a member variable of instance by value of integer or nsnumber type.
If possible, it is easier to set values and read values of any instance.
For example of property part copy.
MyClass *testClass = [[[MyClass alloc] init] autorelease];
testClass.year_1 = #2012;
testClass.quarter_2 = #3;
testClass.month_3 = #8;
testClass.day_4 = #20;
testClass.week_5 = #4;
// copy propertys to other instance.
// Normal way
MyClass *testClassCopy = [[[MyClass alloc] init] autorelease];
testClassCopy.year_1 = testClass.year_1;
testClassCopy.quarter_2 = testClass.quarter_2;
testClassCopy.month_3 = testClass.month_3;
testClassCopy.day_4 = testClass.day_4;
// copy propertys by using wildcard
for (int j = 0; j < 4; j++) {
NSString *indicate = [NSString stringWithFormat:#"*%#", [NSNumber numberWithInteger:j + 1]];
NSNumber *sourceProperty = [testClass valueForKey:indicate];
[testClassCopy setValue:sourceProperty forKey:indicate];
}

Answer 1

I'll raise your wildcards by adding Regex, and by using categories:
To read about how regex works with this, please read the NSRegularExpression Class Reference.
Features:
Uses regex, for matching of a wide variety of keys
Uses a category that works on any instance
Caches key lists per class
Full KVC support (not just properties, but accessor methods & iVars too!)
Integrates flawlessly with current KVC methods (only uses the regex if the key wasn't found, improving performance)
Subclassing doesn't mess it up, like #JamesWebster's solution
Doesn't needlessly pollute the list of keys with NSObject's methods
Returns a NSDictionary of matched keys & values
Cons:
Uses regex, which is slower and more complex to understand
Slow initial lookup for a class (must iterate through all methods & iVars)
Automatically overwrites the -valueForUndefinedKey: method, so it's possible that this could break some existing code (move it to it's own method to fix).
Currently doesn't support setting of values (by design, that's a whole other bag of cats).
Can have duplicate keyPaths in the result (not the biggest of issues, but stems from the fact that KVC matching is complex, and I have to implement all of the rules)
Uses NSRegularExpression, which is only available in iOS 4 and later (not the largest of issues).
Version History:
1.0: Initial Release
So, here is the code:
NSObject+KVCRegex.h:
//
// NSObject+KVCRegex.h
// TestProj
//
// Created by Richard Ross on 8/20/12.
// Copyright (c) 2012 Ultimate Computer Services, Inc. All rights reserved.
//
#import <Foundation/Foundation.h>
#interface NSObject (KVCRegex)
// custom implemenation
-(id) valueForUndefinedKey:(NSString *)key;
#end
NSObject+KVCRegex.m:
//
// NSObject+KVCRegex.m
// TestProj
//
// Created by Richard Ross on 8/20/12.
// Copyright (c) 2012 Ultimate Computer Services, Inc. All rights reserved.
//
#import "NSObject+KVCRegex.h"
#import <objc/runtime.h>
#implementation NSObject (KVCRegex)
static NSSet *keyPathsForClass(Class cls)
{
NSMutableSet *keys = [NSMutableSet set];
do
{
if (cls == [NSObject class])
{
// nothing good can come from trying to use KVC on NSObject methods
break;
}
unsigned count = 0;
Method *methods = class_copyMethodList(cls, &count);
for (int i = 0; i < count; i++) {
// make sure that the method returns a value
const char *methodName = sel_getName(method_getName(methods[i]));
char returnType[64];
method_getReturnType(methods[i], returnType, 64);
if (strcmp(returnType, "v") == 0)
continue;
// make sure that the method takes no args (except for self & _cmd)
if (method_getNumberOfArguments(methods[i]) == 2)
{
// add a duplicate entry for ones matching 'is'
if (strstr(methodName, "is") == methodName)
{
char *newStr = strdup(methodName + 2);
newStr[0] = tolower(newStr[0]);
[keys addObject:[NSString stringWithUTF8String:newStr]];
free(newStr);
}
[keys addObject:[NSString stringWithUTF8String:methodName]];
}
}
free(methods);
// now copy iVars
count = 0;
Ivar *ivars = class_copyIvarList(cls, &count);
for (int i = 0; i < count; i++)
{
const char *ivarName = ivar_getName(ivars[i]);
if (strstr(ivarName, "_") == ivarName)
[keys addObject:[NSString stringWithUTF8String:ivarName + 1]]; // iVar name starting with _<key>
[keys addObject:[NSString stringWithUTF8String:ivarName]];
}
free(ivars);
} while ((cls = [cls superclass]));
return [NSSet setWithSet:keys];
}
// returns a dictionary based on 'key' as a regex
-(id) valueForUndefinedKey:(NSString *)key
{
// lookup for later use
static NSMutableDictionary *keyClassPairs;
if (!keyClassPairs)
keyClassPairs = [NSMutableDictionary dictionary];
if (!keyClassPairs[[self class]])
{
keyClassPairs[(id<NSCopying>)[self class]] = keyPathsForClass([self class]);
}
NSSet *keyPaths = keyClassPairs[[self class]];
// assume 'key' is a regex
NSRegularExpression *regex = [NSRegularExpression regularExpressionWithPattern:key options:0 error:nil];
NSMutableArray *matches = [NSMutableArray array];
for (NSString *keyPath in keyPaths)
{
NSRange matchRange = [regex rangeOfFirstMatchInString:keyPath options:0 range:(NSRange) { 0, keyPath.length }];
if (matchRange.length == keyPath.length)
{
// we have a match
[matches addObject:keyPath];
}
}
if (matches.count)
return [self dictionaryWithValuesForKeys:matches];
else
[NSException raise:NSUndefinedKeyException format:#"Could not find a key that matches the regex in %#", key];
return nil;
}
#end
Example:
#interface MyObject : NSObject
{
#public
int normalIvar;
id _underscoreIvar;
}
#property id someProp;
#property BOOL isProperty;
#property int nativeProp;
-(void) notAKey;
-(id) aKey;
#end
#implementation MyObject
#synthesize someProp, isProperty, nativeProp;
-(void) notAKey
{
NSLog(#"Not a key!");
}
-(id) aKey
{
return #"Value";
}
#end
int main()
{
#autoreleasepool {
MyObject *obj = [MyObject new];
obj.someProp = #"a property";
obj.nativeProp = 15;
obj.isProperty = YES;
obj->normalIvar = 172;
obj->_underscoreIvar = #"Ivar";
NSString *regex = #"[a|s].*"; // match a key starting with 'a' or 's', then matching anything else after
NSLog(#"%#", [obj valueForKey:regex]); // prints "{ aKey = 'Value', someProp = 'a property' }"
regex = #"_.*"; // match a key starting with '_', and then match anything else after
NSLog(#"%#", [obj valueForKey:regex]); // prints "{ _underscoreIvar = 'Ivar' }"
regex = #".*"; // match any key declared for this object
NSLog(#"%#", [obj valueForKey:regex]); // prints "{ "_underscoreIvar" = Ivar; aKey = Value; isProperty = 1; nativeProp = 15; normalIvar = 172; property = 1; someProp = "a property"; underscoreIvar = Ivar; }"
regex = #"(?i)[A-J].*"; // match (case insensitive) a key starting with A - J
NSLog(#"%#", [obj valueForKey:regex]); // prints "{ aKey = value; isProperty = 1; }"
}
}

Answer 2

Though I couldn't find a way to support wildcards using the syntax you were attempting. I found this roundabout method using the Objective-C runtime!
First we get all of the properties of the class you'd like to use
#import <objc/runtime.h>
unsigned int outCount;
objc_property_t *properties = class_copyPropertyList([MyClass class], &outCount);
NSMutableArray *array = [NSMutableArray arrayWithCapacity:outCount];
for (int i = 0; i < outCount; i++)
{
objc_property_t property = properties[i];
const char *propName = property_getName(property);
if(propName)
{
NSString *propertyName = [NSString stringWithUTF8String:propName];
[array addObject:propertyName];
}
}
free(properties);
Then filter out the ones you actually want
NSPredicate *predicate = [NSPredicate predicateWithFormat:#"SELF ENDSWITH '1'"];
[array filterUsingPredicate:predicate];
Then actually use them
for (NSString *key in array)
NSLog(#"%#", [testClass valueForKey:key]);