Given this implementation:
- (NSMutableArray *)programStack
{
if (_programStack == nil)
_programStack = [[NSMutableArray alloc]init];
return _programStack;
}
- (id)program
{
return [self.programStack copy];
}
+ (double)popOperandOffStack:(NSMutableArray *)stack
{
double result = 0;
id topOfStack = [stack lastObject];
if (topOfStack)
[stack removeLastObject];
if ([topOfStack isKindOfClass:[NSNumber class]]) {
result = [topOfStack doubleValue];
}
else if ([topOfStack isKindOfClass:[NSString class]])
{
NSString *operation = topOfStack;
// C
if ([operation isEqualToString:#"C"])
{
[stack removeAllObjects];
return 0;
}
}
}
Am I correct in assuming that the class method's call to [stack removeAllObjects] only affects a copy of a copy rather than removing all objects from the instance's _programStack ? How would you, from that class method, affect the instance's variable? Or is there a better way to do this?
Thanks.
[stack removeAllObjects]; will remove all objects from stack. If you call + (double)popOperandOffStack:(NSMutableArray *)stack from an object, passing an instance variable as stack, then popOperandOffStack: operates on that instance variable and will remove all objects:
[[self class] popOperandOffStack:self.myInstanceArray]
If, on the other hand, you call [[self class] popOperandOffStack:[self.myInstanceArray mutableCopy]] it will operate on a copy.
Related
If I have an object myObject of class id, how would I "cast" it as a CGPoint (given that I have performed introspection and know myObject to a CGPoint)? This is despite the fact that CGPoint is not a real Obj-C class.
Simply doing (CGPoint)myObject returns the following error:
Used type 'CGPoint' (aka 'struct CGPoint') where arithmetic or pointer type is required
I want to do this so that I can check if the object being passed to an NSMutableArray is a CGPoint, and if it is, to wrap the CGPoint in an NSValue automatically; e.g.:
- (void)addObjectToNewMutableArray:(id)object
{
NSMutableArray *myArray = [[NSMutableArray alloc] init];
id objectToAdd = object;
if ([object isKindOfClass:[CGPoint class]]) // pseudo-code, doesn't work
{
objectToAdd = [NSValue valueWithCGPoint:object];
}
[myArray addObject:objectToAdd];
return myArray;
}
ADDITIONAL CODE
Here are the functions I use to perform "introspection":
+ (BOOL)validateObject:(id)object
{
if (object)
{
if ([object isKindOfClass:[NSValue class]])
{
NSValue *value = (NSValue *)object;
if (CGPointEqualToPoint([value CGPointValue], [value CGPointValue]))
{
return YES;
}
else
{
NSLog(#"[TEST] Invalid object: object is not CGPoint");
return NO;
}
}
else
{
NSLog(#"[TEST] Invalid object: class not allowed (%#)", [object class]);
return NO;
}
}
return YES;
}
+ (BOOL)validateArray:(NSArray *)array
{
for (id object in array)
{
if (object)
{
if ([object isKindOfClass:[NSValue class]])
{
NSValue *value = (NSValue *)object;
if (!(CGPointEqualToPoint([value CGPointValue], [value CGPointValue])))
{
NSLog(#"[TEST] Invalid object: object is not CGPoint");
return NO;
}
}
else
{
NSLog(#"[TEST] Invalid object: class not allowed (%#)", [object class]);
return NO;
}
}
}
return YES;
}
+ (NSValue *)convertObject:(CGPoint)object
{
return [NSValue valueWithCGPoint:object];
}
A CGPoint is not an Objective-C object. You cannot pass one to your addObjectToNewMutableArray: method. The compiler will not let you.
You need to wrap the CGPoint in an NSValue and pass that wrapper to your addObjectToNewMutableArray: method.
If you have an NSValue and you want to test whether it contains a CGPoint, you can ask it like this:
if (strcmp([value objCType], #encode(CGPoint)) == 0) {
CGPoint point = [value CGPointValue];
...
}
a point isnt an object and therefore cant be cast to one...
or vice-versa
casting doesnt transform data it only changes how data is interpreted!
id is basically short for NSObject* btw
Im working with a singleton to store some data, her's the implementation
static ApplicationData *sharedData = nil;
#implementation ApplicationData
#synthesize list;
+ (id)sharedData
{
static dispatch_once_t dis;
dispatch_once(&dis, ^{
if (sharedData == nil) sharedData = [[self alloc] init];
});
return sharedData;
}
- (id)init
{
if (self = [super init])
{
list = [[NSMutableArray alloc]init];
}
return self;
}
if list have less than 3 (2<) object i the app crash with "index 0 beyond bounds for empty array"
// NSMutableArray *anArray = [[NSMutableArray alloc]initWithObjects:#"", nil];
while ([[[ApplicationData sharedData]list] lastObject] != nil)
{
File *file = [[[ApplicationData sharedData]list] lastObject];
BOOL isDir;
if (![[NSFileManager defaultManager] fileExistsAtPath:file.filePath isDirectory:&isDir])
{
NSMutableDictionary *tmpDic = [NSMutableDictionary dictionaryWithObjects:[NSArray arrayWithObjects:file.fileName,file.filePath,logEnteryErrorfileNotFoundDisplayName,[formatter stringFromDate:[NSDate date]], nil] forKeys:[NSArray arrayWithObjects:logShredFileName,logShredFilePath,logShredStatue,logShredDate, nil]];
[logArray addObject:tmpDic];
errorOccured = YES;
[[[ApplicationData sharedData]list] removeLastObject];
continue;
}
... other code
}
if i use the anArray that work perfectly.
what is the problem ?
That's totally weird, you've probably did something else to achieve this. Why don't you use - (void)removeAllObjects?
Maybe you remove objects in the while cycle the last line, ie:
while ([[[ApplicationData sharedData]list] count] != 0)
{
// remove object from list
// ...
[[[ApplicationData sharedData]list] removeLastObject];
}
And just a note, you don't need to check if (sharedData == nil) in sharedData as far as it's guaranteed to be executed only once. (unless you do something outside to your static variable, but that's not how it's supposed to be done I believe)
This question already has an answer here:
Closed 10 years ago.
Possible Duplicate:
'isMemberOfClass' returning 'NO' when custom init
I've some trouble with the "isMemberOfClass"-Method.
I have a class, that generates and returns objects ("MyObject")
// ObjectFactory.h
...
-(MyObject*)generateMyObject;
...
// ObjectFactory.m
...
-(MyObject*)generateMyObject
{
MyObject *obj = [[MyObject alloc]init];
obj.name = #"Whatever"; // set properties of object
return obj;
}
...
And there's a unittest-class, that calls the generateMyObject-selector and checks the class of the returned object:
...
ObjectFactory *factory = [[ObjectFactory alloc]init];
MyObject *obj = [factory generateMyObject];
if (![obj isMemeberOfclass:[MyObject class]])
STFail(#"Upps, object of wrong class returned...");
else
...
I expect, that the else-part is processed...but the STFail(...) is called instead, but why?
Thx for any help!
Regards,
matrau
Ok, here is the original copy&pasted code:
//testcase
- (void)test001_setCostumeFirstCostume
{
NSString *xmlString = #"<Bricks.SetCostumeBrick><costumeData reference=\"../../../../../costumeDataList/Common.CostumeData\"/><sprite reference=\"../../../../..\"/></Bricks.SetCostumeBrick>";
NSError *error;
NSData *xmlData = [xmlString dataUsingEncoding:NSASCIIStringEncoding];
GDataXMLDocument *doc = [[GDataXMLDocument alloc] initWithData:xmlData
options:0 error:&error];
SetCostumeBrick *newBrick = [self.parser loadSetCostumeBrick:doc.rootElement];
if (![newBrick isMemberOfClass:[SetCostumeBrick class]])
STFail(#"Wrong class-member");
}
// "MyObject"
#implementation SetCostumeBrick
#synthesize indexOfCostumeInArray = _indexOfCostumeInArray;
- (void)performOnSprite:(Sprite *)sprite fromScript:(Script*)script
{
NSLog(#"Performing: %#", self.description);
[sprite performSelectorOnMainThread:#selector(changeCostume:) withObject:self.indexOfCostumeInArray waitUntilDone:true];
}
- (NSString*)description
{
return [NSString stringWithFormat:#"SetCostumeBrick (CostumeIndex: %d)", self.indexOfCostumeInArray.intValue];
}
#end
// superclass of SetCostumeBrick
#implementation Brick
- (NSString*)description
{
return #"Brick (NO SPECIFIC DESCRIPTION GIVEN! OVERRIDE THE DESCRIPTION METHOD!";
}
//abstract method (!!!)
- (void)performOnSprite:(Sprite *)sprite fromScript:(Script*)script
{
#throw [NSException exceptionWithName:NSInternalInconsistencyException
reason:[NSString stringWithFormat:#"You must override %# in a subclass", NSStringFromSelector(_cmd)]
userInfo:nil];
}
#end
// the "factory" (a xml-parser)
- (SetCostumeBrick*)loadSetCostumeBrick:(GDataXMLElement*)gDataSetCostumeBrick
{
SetCostumeBrick *ret = [[SetCostumeBrick alloc] init];
NSArray *references = [gDataSetCostumeBrick elementsForName:#"costumeData"];
GDataXMLNode *temp = [(GDataXMLElement*)[references objectAtIndex:0]attributeForName:#"reference"];
NSString *referencePath = temp.stringValue;
if ([referencePath length] > 2)
{
if([referencePath hasSuffix:#"]"]) //index found
{
NSString *indexString = [referencePath substringWithRange:NSMakeRange([referencePath length]-2, 1)];
ret.indexOfCostumeInArray = [NSNumber numberWithInt:indexString.intValue-1];
}
else
{
ret.indexOfCostumeInArray = [NSNumber numberWithInt:0];
}
}
else
{
ret.indexOfCostumeInArray = nil;
#throw [NSException exceptionWithName:NSInternalInconsistencyException
reason:[NSString stringWithFormat:#"Parser error! (#1)"]
userInfo:nil];
}
NSLog(#"Index: %#, Reference: %#", ret.indexOfCostumeInArray, [references objectAtIndex:0]);
return ret;
}
SOLUTION:
Eiko/jrturton gave me a link to the solution - thx: isMemberOfClass returns no when ViewController is instantiated from UIStoryboard
The problem was, that the classes were included in both targets (app and test bundle)
Thank you guys for your help :)
You generally want isKindOfClass:, not isMemberOfClass. The isKindOfClass: will return YES if the receiver is a member of a subclass of the class in question, whereas isMemberOfClass: will return NO in the same case.
if ([obj isKindOfClass:[MyObject class]])
For example,
NSArray *array = [NSArray array];
Here [array isMemberOfClass:[NSArray class]] will return NO but [array isKindOfClass:[NSArray class]] will return YES.
Ok, with different class addresses per your comment, I think I can track this down to be a duplicate of this:
isMemberOfClass returns no when ViewController is instantiated from UIStoryboard
Basically, your class is included twice.
below is a class method that always returns null -when, for example, stack = 2,2,"+" I want it to return "2+2"
In the initial iteration the method correctly determines the topOfStack is a NSString rather than a NSNumber but is doesn't create NSString 'description' to equal "2+2" by recursive calling
I feel I'm missing something obvious here, am I dealing with the strings correctly....
+ (NSString *) descriptionOfTopOfStack: (NSMutableArray * ) stack
{
NSString *description;
id topOfStack = [stack lastObject]; // get last object
if (topOfStack) [stack removeLastObject]; // then remove it from stack
if ([topOfStack isKindOfClass:[NSNumber class]]) { // is last object a number?
return [topOfStack stringValue]; // if so then return it, **done***
}
else if ([topOfStack isKindOfClass:[NSString class]])
{
if ([topOfStack isEqualToString:#"+"])
{
[description stringByAppendingString: [self descriptionOfTopOfStack:stack]];
[description stringByAppendingString:#"+"];
[description stringByAppendingString: [self descriptionOfTopOfStack:stack]];
}
}
NSLog(#"Description is %#", description);
return description;
}
Method stringByAppendingString: returns an autoreleased string, does not modify the original one. If you want to modify description you must do something like
description = [description stringByAppendingString: [self descriptionOfTopOfStack:stack]];
Besides, writing
NSString *description;
you are just creating a pointer to a NSString, not a NSString. Use instead
NSString* description = #"";
I'm curious, I currently have an NSDictionary where some values are set to an NSNull object thanks to the help of json-framework.
The aim is to strip all NSNull values and replace it with an empty string.
I'm sure someone has done this somewhere? No doubt it is probably a four liner and is simple, I am just far too burnt out to figure this out on my own.
I've made a few changes to Jacob's original answer to extend it to handle dictionaries and arrays stored within the original dictionary.
#import "NSDictionary+NullReplacement.h"
#import "NSArray+NullReplacement.h"
#implementation NSDictionary (NullReplacement)
- (NSDictionary *)dictionaryByReplacingNullsWithBlanks {
const NSMutableDictionary *replaced = [self mutableCopy];
const id nul = [NSNull null];
const NSString *blank = #"";
for (NSString *key in self) {
id object = [self objectForKey:key];
if (object == nul) [replaced setObject:blank forKey:key];
else if ([object isKindOfClass:[NSDictionary class]]) [replaced setObject:[object dictionaryByReplacingNullsWithBlanks] forKey:key];
else if ([object isKindOfClass:[NSArray class]]) [replaced setObject:[object arrayByReplacingNullsWithBlanks] forKey:key];
}
return [NSDictionary dictionaryWithDictionary:[replaced copy]];
}
#end
And there's also an array category of course:
#import "NSArray+NullReplacement.h"
#import "NSDictionary+NullReplacement.h"
#implementation NSArray (NullReplacement)
- (NSArray *)arrayByReplacingNullsWithBlanks {
NSMutableArray *replaced = [self mutableCopy];
const id nul = [NSNull null];
const NSString *blank = #"";
for (int idx = 0; idx < [replaced count]; idx++) {
id object = [replaced objectAtIndex:idx];
if (object == nul) [replaced replaceObjectAtIndex:idx withObject:blank];
else if ([object isKindOfClass:[NSDictionary class]]) [replaced replaceObjectAtIndex:idx withObject:[object dictionaryByReplacingNullsWithBlanks]];
else if ([object isKindOfClass:[NSArray class]]) [replaced replaceObjectAtIndex:idx withObject:[object arrayByReplacingNullsWithBlanks]];
}
return [replaced copy];
}
#end
With this, you can take any array or dictionary and recursively wipe out all the [NSNull null] instances.
P.S. For completion's sake, here are the header files:
#interface NSDictionary (NullReplacement)
- (NSDictionary *)dictionaryByReplacingNullsWithBlanks;
#end
And the array header:
#interface NSArray (NullReplacement)
- (NSArray *)arrayByReplacingNullsWithBlanks;
#end
Really simple:
#interface NSDictionary (JRAdditions)
- (NSDictionary *)dictionaryByReplacingNullsWithStrings;
#end
#implementation NSDictionary (JRAdditions)
- (NSDictionary *)dictionaryByReplacingNullsWithStrings {
const NSMutableDictionary *replaced = [self mutableCopy];
const id nul = [NSNull null];
const NSString *blank = #"";
for(NSString *key in self) {
const id object = [self objectForKey:key];
if(object == nul) {
//pointer comparison is way faster than -isKindOfClass:
//since [NSNull null] is a singleton, they'll all point to the same
//location in memory.
[replaced setObject:blank
forKey:key];
}
}
return [replaced copy];
}
#end
Usage:
NSDictionary *someDictThatHasNulls = ...;
NSDictionary *replacedDict = [someDictThatHasNulls dictionaryByReplacingNullsWithStrings];
Rolling through the dictionary hunting for NSNull is one way to tackle the problem, but I took a slightly lazier approach. Instead of nil you could assign an empty string, but the principle is the same.
CPJSONDictionary.h
#interface NSDictionary (CPJSONDictionary)
- (id)jsonObjectForKey:(id)aKey;
#end
CPJSONDictionary.m
#implementation NSDictionary (CPJSONDictionary)
- (id)jsonObjectForKey:(id)aKey {
id object = [self objectForKey:aKey];
if ([object isKindOfClass:[NSNull class]]) {
object = nil;
}
return object;
}
#end
I have tested Stakenborg solution. It works well, but it has following problem. If some object is expected to be number, for instance, converting it to NSNull can be a source of error.
I have create a new method to directly remove the NSNull entries. This way you only have to check that correspondant key exists.
Add in NSDictionary+NullReplacement
- (NSDictionary *)dictionaryByRemovingNulls{
const NSMutableDictionary *replaced = [self mutableCopy];
const id nul = [NSNull null];
for (NSString *key in self) {
id object = [self objectForKey:key];
if (object == nul) [replaced removeObjectForKey:key];
else if ([object isKindOfClass:[NSDictionary class]]) [replaced setObject:[object dictionaryByRemovingNulls] forKey:key];
else if ([object isKindOfClass:[NSArray class]]) [replaced setObject:[object arrayByRemovingNulls] forKey:key];
}
return [NSDictionary dictionaryWithDictionary:[replaced copy]];
}
And in NSArray+NullReplacement
- (NSArray *)arrayByRemovingNulls {
NSMutableArray *replaced = [self mutableCopy];
const id nul = [NSNull null];
for (int idx = [replaced count]-1; idx >=0; idx--) {
id object = [replaced objectAtIndex:idx];
if (object == nul) [replaced removeObjectAtIndex:idx];
else if ([object isKindOfClass:[NSDictionary class]]) [replaced replaceObjectAtIndex:idx withObject:[object dictionaryByRemovingNulls]];
else if ([object isKindOfClass:[NSArray class]]) [replaced replaceObjectAtIndex:idx withObject:[object arrayByRemovingNulls]];
}
return [replaced copy];
}
another variation:
NSDictionary * NewDictionaryReplacingNSNullWithEmptyNSString(NSDictionary * dict) {
NSMutableDictionary * const m = [dict mutableCopy];
NSString * const empty = #"";
id const nul = [NSNull null];
NSArray * const keys = [m allKeys];
for (NSUInteger idx = 0, count = [keys count]; idx < count; ++idx) {
id const key = [keys objectAtIndex:idx];
id const obj = [m objectForKey:key];
if (nul == obj) {
[m setObject:empty forKey:key];
}
}
NSDictionary * result = [m copy];
[m release];
return result;
}
The result is the same as, and it appears pretty much identical to Jacob's, but the speed and memory requirements are one half to one third (ARC or MRC) in the tests I made. Of course, you could also use it as a category method as well.
Here is my solution:
+ (NSDictionary *)cleanNullInJsonDic:(NSDictionary *)dic
{
if (!dic || (id)dic == [NSNull null])
{
return dic;
}
NSMutableDictionary *mulDic = [[NSMutableDictionary alloc] init];
for (NSString *key in [dic allKeys])
{
NSObject *obj = dic[key];
if (!obj || obj == [NSNull null])
{
// [mulDic setObject:[#"" JSONValue] forKey:key];
}else if ([obj isKindOfClass:[NSDictionary class]])
{
[mulDic setObject:[self cleanNullInJsonDic:(NSDictionary *)obj] forKey:key];
}else if ([obj isKindOfClass:[NSArray class]])
{
NSArray *array = [BasicObject cleanNullInJsonArray:(NSArray *)obj];
[mulDic setObject:array forKey:key];
}else
{
[mulDic setObject:obj forKey:key];
}
}
return mulDic;
}
+ (NSArray *)cleanNullInJsonArray:(NSArray *)array
{
if (!array || (id)array == [NSNull null])
{
return array;
}
NSMutableArray *mulArray = [[NSMutableArray alloc] init];
for (NSObject *obj in array)
{
if (!obj || obj == [NSNull null])
{
// [mulArray addObject:[#"" JSONValue]];
}else if ([obj isKindOfClass:[NSDictionary class]])
{
NSDictionary *dic = [self cleanNullInJsonDic:(NSDictionary *)obj];
[mulArray addObject:dic];
}else if ([obj isKindOfClass:[NSArray class]])
{
NSArray *a = [BasicObject cleanNullInJsonArray:(NSArray *)obj];
[mulArray addObject:a];
}else
{
[mulArray addObject:obj];
}
}
return mulArray;
}
-(NSDictionary*)stripNulls:(NSDictionary*)dict{
NSMutableDictionary *returnDict = [NSMutableDictionary new];
NSArray *allKeys = [dict allKeys];
NSArray *allValues = [dict allValues];
for (int i=0; i<[allValues count]; i++) {
if([allValues objectAtIndex:i] == (NSString*)[NSNull null]){
[returnDict setValue:#"" forKey:[allKeys objectAtIndex:i]];
}
else
[returnDict setValue:[allValues objectAtIndex:i] forKey:[allKeys objectAtIndex:i]];
}
return returnDict;
}
A category on nsnull that returns nil seems to also sense, at least to me. There are a few out there. One makes all calls return nil which seems to make sense. Sorry no link. I guess if you need to later use nspropertylistserialization the category might not work for you.