I have this macro that detects if a variable is an object:
#define IS_OBJECT(x) ( strchr("##", #encode(typeof(x))[0]) != NULL )
#define AUTO_BOX(x) IS_OBJECT(x) ? x : #(x)
I wanted to simplify my workflow by auto box any primitives so that I can quickly do something like this:
BOOL v1 = YES;
id v2 = [[NSObject alloc] init];
NSLog(#"%# %#", AUTO_BOX(v1), AUTO_BOX(v2));
//the #"%# %#" format is non-changeable, I can't change them to #"%d %#" or #"%x %#"
This of course will throw error for v2 since it's an object:
error: illegal type 'id' used in a boxed expression
What could I do to fix this?
CF_INLINE id auto_box_id_helper(const char *type, __strong id* val) {
return *val;
}
CF_INLINE id auto_box_default_helper(const char *type, void *ptr) {
return [NSValue valueWithBytes:ptr objCType:type];
}
#define AUTO_BOX(x) _Generic(\
(x),\
id: auto_box_id_helper,\
default: auto_box_default_helper\
)(\
#encode(typeof((x))),\
(typeof((x))[1]){(x)}\
)
(typeof((x))[1]){(x)} is used instead of &(x), because you can't get pointer for example from &5. Also you will need expand this macro with NSNumber parameters, if you want get NSNumber instead of NSValue for numbers.
Related
I am trying to get data from web service and adding it into nsmutablearray,
after that i want to return that array from extern c function.....
for example:
#implementation SampleClass
-(NSMutableArray* ) createArray:
{
NSMutableArray *array=[NSMutableArray new];
//
//add value in array
//
return array;
}
#end
extern 'C'
{
//how can i
NSArray* returnArray()// this method should return string array
{
SampleClass *sc=[[SampleClass alloc]init];
NSMUtableArray* a=[NSMutableArray new];
a=[sc createArray];
return a
}
}
#end
Why would you need to use extern "C" since Objective-C is a superset of C? You can already use C code without problems.
For your question it depends on lifetime of the array. If the array is retained then this is enough:
char *cString = [[array objectAtIndex:i] UTF8String];
Otherwise you'd need to allocate a new char* for each string, for example by using strdup:
char *cString = strdup([[array objectAtIndex:i] UTF8String]);
Mind that the latter will require you to release memory when you longer need it with free(cString). If you need to return a C array then you will create it before and set values accordingly, eg
char** cArray = calloc([array count], sizeof(char*));
I need a way to pass a property and get the name assigned to it. Any suggestions?
#property (nonatomic, retain) MyObject *crazyObject;
NSString *str = SOME_WAY_TO_GET_PROPERTY_NAME(crazyObject);
// Above method should return #"crazyObject"
You can try this:
unsigned int propertyCount = 0;
objc_property_t * properties = class_copyPropertyList([self class], &propertyCount);
NSMutableArray * propertyNames = [NSMutableArray array];
for (unsigned int i = 0; i < propertyCount; ++i) {
objc_property_t property = properties[i];
const char * name = property_getName(property);
[propertyNames addObject:[NSString stringWithUTF8String:name]];
}
free(properties);
NSLog(#"Names: %#", propertyNames);
It's as simple as this...expanding upon what Chuck already mentioned:
#ifndef STR_PROP
#define STR_PROP( prop ) NSStringFromSelector(#selector(prop))
#endif
You then use it like so:
NSString *strProp = STR_PROP(myProperty);
Background
Keep in mind that properties are really just, to quote Apple, "a syntactical shorthand for declaring a class’s accessor methods." In fact, by itself, the #property declaration doesn't even work. Your #synthesize statement translates the #property into the equivalent of two methods:
- (void)setCrazyObject:(MyObject *)something;
- (MyObject *)crazyObject;
Which one is used depends on the context surrounding your self.crazyObject. (#synthesize also creates a matching instance variable if you didn't do it yourself.) The offshoot of all this is that you can't really translate to and from a property with one single method.
Proposed Solution
You can use what Apple already provides:
NSString *foo = NSStringFromSelector(#selector(myClassProperty));
Or do something custom:
Given that self.crazyObject really translates to either [self crazyObject] or [self setCrazyObject:foo] by the time your code is running, ou'll probably need two methods, like:
- (NSString *)setterStringForProperty:(SEL)prop;
- (NSString *)getterStringForProperty:(SEL)prop;
You might then want at least 2 companion methods such as:
- (SEL)setterForPropertyName:(NSString *)propString;
- (SEL)getterForPropertyName:(NSString *)propString;
Within these methods, you can use the Foundation functions NSStringFromSelector and NSSelectorFromString to convert back and forth between SEL and NSString. Use whatever string manipulations you like to convert back and forth between your setter string (setCrazyObject) and your property name (crazyObject).
A complete solution is hard to provide without knowing the exact use case, but hopefully this provides some more clues for anyone trying to accomplish something similar. There might even be some useful things made possible by combining this approach with Oscar's answer.
Here is a function that returns the name of an ivar, so basically it not only returns the properties but any ivar of the class. I haven't found a way to get the property directly so I used the ivar trick.
#import <objc/objc.h>
/// -----
- (NSString *)nameOfIvar:(id)ivarPtr
{
NSString *name = nil;
uint32_t ivarCount;
Ivar *ivars = class_copyIvarList([self class], &ivarCount);
if(ivars)
{
for(uint32_t i=0; i<ivarCount; i++)
{
Ivar ivar = ivars[i];
id pointer = object_getIvar(self, ivar);
if(pointer == ivarPtr)
{
name = [NSString stringWithUTF8String:ivar_getName(ivar)];
break;
}
}
free(ivars);
}
return name;
}
After searching and debugging i find solution for me...
Added #import <objc/runtime.h>
Methods object_getIvar(id obj, Ivar ivar) send bad access and app crashes. i modify some code and it worked great:
+(NSString*)stringWithProperty:(id)property withClass:(id)controller
{
NSString *name = nil;
uint32_t ivarCount;
Ivar *ivars = class_copyIvarList([controller class], &ivarCount);
if(ivars)
{
for(uint32_t i=0; i<ivarCount; i++)
{
Ivar ivar = ivars[i];
name = [NSString stringWithUTF8String:ivar_getName(ivar)];
if ([controller valueForKey:name] == property)
{
break;
}
}
free(ivars);
}
return name;
}
Modifying the solution, it works when your object is allocated already, otherwise it returns nil:-
NSString * NSStringFromProperty(NSObject* property, NSObject* class)
{
unsigned int propertyCount = 0;
objc_property_t * properties = class_copyPropertyList([class class], &propertyCount);
NSString *name = nil;
for (unsigned int i = 0; i < propertyCount; ++i)
{
name = [NSString stringWithUTF8String:property_getName(properties[i])];
NSObject *object = [class valueForKey:name];
if (object != nil && object == property)
{
break;
}
else
{
name = nil;
}
}
free(properties);
return name;
}
You can use
NSString *str = NSStringFromSelector(#selector(crazyObject));
The good thing about this approach is that:
Xcode will autocomplete word crazyObject for you.
When later on you will change the property name from crazyObject to myCrazyObject, Xcode will add a warning saying "unrecognized selector!" -- pretty good for debugging.
I use this method so often, that I even created a function, which allows to write less letters:
NSString * __nonnull sfs(SEL __nonnull theSelector)
{
if (!theSelector)
{
abort();
}
return NSStringFromSelector(theSelector);
}
Now your final solution can look like this:
NSString *str = sfs(#selector(crazyObject));
From Get property name as string, without using the runtime reference library, just define:
#define propertyKeyPath(property) (#""#property)
#define propertyKeyPathLastComponent(property) [[(#""#property) componentsSeparatedByString:#"."] lastObject]
And then you can do something like this:
NSLog(#"%#", propertyKeyPathLastComponent(appleStore.storeLocation.street)); //result: street
You may check my approach at Gist to get the string for a property with autocompletion and compile-time check.
How to use:
Get the property name for a class:
#interface AnyClass : NSObject
#property (strong) NSData *data;
#end
// == My approach ==
// C string for a class
PropertyNameForClass(AnyClass, data); // ==> "data"
// NSString for a class
PropertyStringForClass(AnyClass, data); // ==> #"data"
// Bad approach (no autocompletion; no compile-time check):
NSString *propertyName = #"data";
Get the property name for a protocol:
#protocol AnyProtocol
#property (strong) NSDate *date;
#end
// C string for a protocol
PropertyNameForProtocol(AnyProtocol, date); // ==> "date"
// NSString for a protocol
PropertyStringForProtocol(AnyProtocol, date); // ==> #"date"
Unconventional, hacky, ugly, late, but... as strong-named as it gets and works like a charm:
#define SOME_WAY_TO_GET_PROPERTY_NAME(p) p == p ? [[[[[[[NSString alloc] initWithCString:#p encoding:NSUTF8StringEncoding] componentsSeparatedByString:#"."] lastObject] componentsSeparatedByString:#" "] lastObject] stringByReplacingOccurrencesOfString:#"]" withString:#""] : #""
Sample usage:
NSLog(SOME_WAY_TO_GET_PROPERTY_NAME(self.customer.surname)); // surname
NSLog(SOME_WAY_TO_GET_PROPERTY_NAME([[self customer] birthDate])); // birthDate
...
I've written a macro in Objective-C to perform a safe cast. Here's what it looks like so far:
#define SAFE_CAST(OBJECT, TYPE) ([OBJECT isKindOfClass:[TYPE class]] ? (TYPE *) OBJECT: nil)
This works really well, but it'd be nice if there was a way to store OBJECT in a variable so it didn't get called twice. For instance, using the macro as such:
NSString *str = SAFE_CAST([dictinary objectForKey:key], NSString);
results in code similar to this when the macro is expanded:
NSString *str = ([[dictinary objectForKey:key] isKindOfClass:[NSString class]] ? (NSString *) [dictinary objectForKey:key]: nil);
I'd prefer for it to work more like this:
id obj = [dictionary objectForKey:key];
NSString *str = ([obj objectForKey:key] isKindOfClass[NSString class]] ? (NSString *) obj : nil);
Thanks.
You can use a GCC extension called statement statement expressions to have
#define SAFE_CAST(OBJECT, TYPE) ({ id obj=OBJECT;[obj isKindOfClass:[TYPE class]] ? (TYPE *) obj: nil; })
That said, I think it's generally a bad approach to have a situation where you need to use SAFE_CAST a lot.
Never put objects of different classes in an array; never reuse an action message (IBAction)someAction:(id)sender for UI objects of different classes. Then you usually don't need to use SAFE_CAST.
If you really think you must do this, you could use a function:
#define SAFE_CAST(Object, Type) (Type *)cast_helper(Object, [Type class])
static id cast_helper(id x, Class c) {
return [x isKindOfClass:c] ? x : nil;
}
So write it like that, just wrap it in do { } while(0) <-- and not just in parenthesis.
#define SAFE_CAST(OBJECT, TYPE, VAR) do { \
id obj = OBJECT; \
VAR = [obj isKindOfClass:[TYPE class]] ? (TYPE *) obj : nil; \
} while(0)
I want to get the type of NSNumber instance.
I found out on http://www.cocoadev.com/index.pl?NSNumber this:
NSNumber *myNum = [[NSNumber alloc] initWithBool:TRUE];
if ([[myNum className] isEqualToString:#"NSCFNumber"]) {
// process NSNumber as integer
} else if ([[myNum className] isEqualToString:#"NSCFBoolean"]) {
// process NSNumber as boolean
}
Ok, but this doesn't work, the [myNum className] isn't recognized by the compiler.
I'm compiling for iPhone.
I recommend using the -[NSNumber objCType] method.
It allows you to do:
NSNumber * n = [NSNumber numberWithBool:YES];
if (strcmp([n objCType], #encode(BOOL)) == 0) {
NSLog(#"this is a bool");
} else if (strcmp([n objCType], #encode(int)) == 0) {
NSLog(#"this is an int");
}
For more information on type encodings, check out the Objective-C Runtime Reference.
You can get the type this way, no string comparisons needed:
CFNumberType numberType = CFNumberGetType((CFNumberRef)someNSNumber);
numberType will then be one of:
enum CFNumberType {
kCFNumberSInt8Type = 1,
kCFNumberSInt16Type = 2,
kCFNumberSInt32Type = 3,
kCFNumberSInt64Type = 4,
kCFNumberFloat32Type = 5,
kCFNumberFloat64Type = 6,
kCFNumberCharType = 7,
kCFNumberShortType = 8,
kCFNumberIntType = 9,
kCFNumberLongType = 10,
kCFNumberLongLongType = 11,
kCFNumberFloatType = 12,
kCFNumberDoubleType = 13,
kCFNumberCFIndexType = 14,
kCFNumberNSIntegerType = 15,
kCFNumberCGFloatType = 16,
kCFNumberMaxType = 16
};
typedef enum CFNumberType CFNumberType;
If all you want is to differentiate between booleans and anything else, you can make use of the fact that boolean NSNumbers always return a shared instance:
NSNumber *num = ...;
if (num == (void*)kCFBooleanFalse || num == (void*)kCFBooleanTrue) {
// num is boolean
} else {
// num is not boolean
}
NSNumber explicitly doesn't guarantee that the returned type will match the method used to create it, so doing this at all is probably a bad idea.
However, you could probably do something like this (you could also compare to objc_getClass("NSCFNumber") etc., but this is arguably more portable):
Class boolClass = [[NSNumber numberWithBool:YES] class];
/* ... */
if([myNum isKindOfClass:boolClass]) {
/* ... */
}
In Swift:
let numberType = CFNumberGetType(answer)
switch numberType {
case .charType:
//Bool
case .sInt8Type, .sInt16Type, .sInt32Type, .sInt64Type, .shortType, .intType, .longType, .longLongType, .cfIndexType, .nsIntegerType:
//Int
case .float32Type, .float64Type, .floatType, .doubleType, .cgFloatType:
//Double
}
Use the method -[NSNumber objCType] method to get the type.
If the type's equal to #encode(BOOL), or the number itself is kCFBooleanFalse, or kCFBooleanTrue, it's a boolean.
If it's anything else but 'c', it's a number.
If it's 'c', what appears to be the only way supported way, without checking against private class names, or comparing against undocumented singletons, is to turn make an array of one element, the number, and then use NSJSONSerialization to get the string representation. Finally, check if the string representation contains the string "true" or "false". Here is the full code for checking if an NSNumber is a BOOL:
-(BOOL)isBool
{
if(!strcmp(self.objCType, #encode(BOOL)) ||
self == (void*)kCFBooleanFalse ||
self == (void*)kCFBooleanTrue)
{
return YES;
}
if(strcmp(self.objCType, "c"))
{
return NO;
}
NSString * asString = [[NSString alloc] initWithData:[NSJSONSerialization dataWithJSONObject:#[self] options:kNilOptions error:nil] encoding:NSUTF8StringEncoding];
return [asString containsString:#"true"] || [asString containsString:#"false"];
}
Note that using NSJSONSerialization is slow and if #NO/#YES ever stops always equalling kCFBooleanFalse/kCFBooleanTrue, then this method probably shouldn't be used in a tight loop.
The reason the compiler warns you and it doesn't work is because -[NSObject className] is declared in a category on NSObject on Mac OS X (in NSScriptClassDescription.h) and not declared on iPhone. (It doesn't support AppleScript, obviously.) NSStringFromClass([myNum class]) is what you should use to be safe across all platforms. Odds are that -className is declared as a simple wrapper around NSStringFromClass() anyway...
NSString *classString = NSStringFromClass([myNum class]);
That should ger the string you want.
To check that NSNumber contains a bool value Try this:
if (strcmp([myNumber objCType], [#(YES) objCType]) == 0)
NSLog(#"%#", [myNumber boolValue] ? #"true" : #"false");
objCType documentation states that The returned type does not necessarily match the method the number object was created with
Secondly, other methods of comparing the class of number to a given class type or assuming boolean number instances to be shared singletons are not documented behaviour.
A more(not completely though) reliable way is to depend on NSJSONSerialisation as it correctly recognises number instances created with bool and outputs true/false in json. This is something we can expect Apple to take care of while moving with new SDKs and on different architectures. Below is the code:
+(BOOL) isBoolType:(NSNumber*) number {
NSError* err;
NSData* jsonData = [NSJSONSerialization dataWithJSONObject:#{#"key":number}
options:0
error:&err];
NSString* jsonString = [[NSString alloc]
initWithData:jsonData
encoding:NSUTF8StringEncoding];
return [jsonString containsString:#"true"]
|| [jsonString containsString:#"false"];
}
Swift Version
NSNumber is a class-cluster so each underlying type can be figured from the instance. This code avoids hard-coding the different NSNumber types by creating an instance of the expected type, and then comparing it against the unknown type.
extension NSNumber {
var isBool: Bool {
return type(of: self) == type(of: NSNumber(booleanLiteral: true))
}
}
check object is of NSNumber type :
if([obj isKindOfClass:NSClassFromString(#"__NSCFNumber")])
{
//NSNumber
}
Say I have my class
#interface Person : NSObject { NSString *name; }
I need to get the name of NSString's within my class
Person *person = [[Person alloc] init];
NSLog(#"Name of variable %s\n", _NameofVariable_(person->name));
Thanks for the answers, here's the solution I came up from the replies
//returns nil if property is not found
-(NSString *)propertyName:(id)property {
unsigned int numIvars = 0;
NSString *key=nil;
Ivar * ivars = class_copyIvarList([self class], &numIvars);
for(int i = 0; i < numIvars; i++) {
Ivar thisIvar = ivars[i];
if ((object_getIvar(self, thisIvar) == property)) {
key = [NSString stringWithUTF8String:ivar_getName(thisIvar)];
break;
}
}
free(ivars);
return key;
}
As easy as
#define VariableName(arg) (#""#arg)
Then you do:
NSObject *obj;
NSString *str = VariableName(obj);
NSLog(#"STR %#", str);//obj
You can get the names of a class's instance variables with the Objective-C runtime API function class_copyIvarList. However, this is rather involved, rarely done and almost never the best way to accomplish something. If you have a more specific goal in mind than mere curiosity, it might be a good idea to ask about how to accomplish it in Objective-C.
Also, incidentally, person.name doesn't specify an instance variable in Objective-C — it's a property call. The instance variable would be person->name.
You might use preprocessor stringification and a bit of string twiddling:
NSUInteger lastIndexAfter(NSUInteger start, NSString *sub, NSString *str) {
NSRange found = [str rangeOfString:sub options:NSBackwardsSearch];
if(found.location != NSNotFound) {
NSUInteger newStart = NSMaxRange(found);
if(newStart > start)
return newStart;
}
return start;
}
NSString *lastMember(NSString *fullName) {
if(!fullName) return nil;
NSUInteger start = 0;
start = lastIndexAfter(start, #".", fullName);
start = lastIndexAfter(start, #"->", fullName);
return [fullName substringFromIndex: start];
}
#define NSStringify(v) (##v)
#define _NameofVariable_(v) lastMember(NSStringify(v))
If the person object is exposed as a property of the class, you can use objc_msgSend to get the value.
So, if you could access person using
[object person]
You could also do
objc_msgSend(object, "person")
For more details on message sending, including how to pass arguments to methods, see the Objective-C Runtime Programming Guide section on Messaging
The following works as a macro:
#define STRINGIZE(x) #x