Sorry, Objective-C noob here.
in java doing this is very simple. The code is just...
if(ParseObject.has("value"){
//dosomething
}
In objective-c there doesn't seem to be an equivilant to this method.
To get the values out of the PFObject, you can use either the objectForKey: method or the [] subscripting operator.
If there is no object for a given key, you will get nil.
Related
I have problem and i cannot fix it by using google.
I have string array (written in swift). But i have objectiveC files with chart functions.
I need transfer whole swift array into objectiveC file.
Example of array:
for i in 0...11 {
mainSelectionMonthArrayValues.append(
String(WatchlistViewController().fetchDataMonth(
type:1, month: i+1, year: 2017)
)
)
}
Given you are not very specific about the code that "does not work" or the specific error you get it is hard to answer anything precisely. But given what Google finds in books for "cocoa pass swift string array to objective-c" you will have
To call an NSArray function on a Swift array you may have to cast to NSArray
so it is a pretty safe bet you will have to do this too if you want to pass mainSelectionMonthArrayValues to an Objective-C method (with an appropriate interface). Casting to an Objective-C class will not be free in most cases, but it is likely to be a constant time operation. Note however, that you will have to coerce if your object needs to be mutable on the Objective-C end. So try passing your array using something like
objCRef.callObjCMethod(mainSelectionMonthArrayValues as NSArray)
If this again "does not work" then you should provide us with more info on the kind of error you experience.
I'm trying to understand NSLog and how to print to the console in Xcode. I understand that NSLog uses what are called "tokens" to setup the type of variable being referenced to print (I think that's right?). What I need to know is the difference in which tokens to use and what they mean?
For example, after declaring an NSArray like below, I'd want to print the drink names to the console. I could do that like:
NSArray *drinks = #[#"juice", #"water", #"coffee"];
for (NSString *drinkName in drinks) {
NSLog(#"%#", drinkName);
}
So...am I using the #"%#" token because it's an NSString?
I would use #"%i" for an integer, and a #"%f" for a float? What about doubles? If anyone could shed some easy-to-understand beginner's knowledge on NSLog, that would be great! =)
As I understand it, NSLog isn't an Objective C function but a C function built into the foundation of Cocoa. Therefore it conforms to basic C functions with variadic arguments. You can use %# for all objects including NSString. This will in turn call the objects description method and print the appropriate string. Most objects have a rather useful representation already there (e.g. NSArray objects return the descriptions of all their contents)
I'm new to Objective-c and I think this should be really easy but somehow I can't figure it out.
I need to call a method from an object which is stored in an NSArray.
The Java code would be: myArray[0].getMyValue();
So I read on the internet that in Objective-c it should look like this: [[myArray objectAtIndex: 0] getMyValue]. Unfortunately this didn't work.
I found other solutions on the internet but none of them worked.
So I hope you guys could help me out?
Update
I'm getting these two error messages:
No known instance method for selector 'getMyValue'
Sending 'id' to parameter of incompatible type 'CGFloat' (aka 'double')
This doesn't work because Objective-C doesn't know what is the type of the object in the array.
Luckily, Apple has added lightweight generics in Xcode 7, which allow you to create typed arrays. This will of course work only if you intend to have one type of object in the array. The syntax looks like this:
NSArray<NSString *> *stringArray;
If you plan to have objects with different types in the array, then you need to cast the object to your type, to be able to call your method. That would look like this:
[((YourObject *)[myArray objectAtIndex: 0]) getMyValue];
And as #Michael pointed out in the comment, another and nicer way to do this would be:
[((YourObject *)myArray[0]) getMyValue];
Objects are stored with id type in NSArray, so you can cast this object to the object type you want. For instance :
NSNumber *myNumber = (NSNumber *)[NSArray objectAtIndex:0];
[myNumber myMethod];
I don't want to subclass from NSDictionary but I want to get the literal syntax. It means that I am about to save and retrieve the key by using the "[]". I get this question from Parse iOS SDK, the PFObject is not inherited from the NSMutableDictionary. And they are able to use the dictionary literal syntax.
Here is the link from Parse iOS SDK: https://parse.com/docs/ios_guide#objects/iOS.
See for example the good Object Subscripting article at NSHipster. You just need to implement two methods in your class:
- (id)objectForKeyedSubscript:(id <NSCopying>)key;
- (void)setObject:(id)obj forKeyedSubscript:(id <NSCopying>)key;
I am a newbie to Objective-C and I am working on getting a good handle in working with arrays.
According to Apples own documentation NSMutableArray inherits from NSArray. I am seeking to use the method objectAtIndex:i within a for loop. Yet Xcode is claiming that
"Property 'objectAtIndex' not found on object of type
'NSMutableArray'".
Within a for loop I am performing (or seeking to) the following test:
if([self.cards objectAtIndex:i].isChosen){
do something here }
I am certain I not doing this right. It can be frustrating learning the idiosyncrasies of a new programming language. For me Objective C has, so far, borne little resemblance to C++ or C.
Any pointer or assistance would be greatly appreciated.
Thanks in advance
Walt Williams
From your error message, you could not be using the method and parameter correctly. Possibly you're trying to use a dot notation?
Your code should be like:
id object = [array objectAtIndex:index];
where the index comes from your loop and you then use the object.
In addition to Wain's answer, which is correct, but for the sake of completeness, you are using the array and trying to call the method this way:
Ex:
array.objectAtIndex.i = 5; //Java.....?
which is the cause of this error:
"Property 'objectAtIndex' not found on object of type
'NSMutableArray'".
It is complaining that you are trying to access a property named "objectAtIndex", which of course, doesn't exist.
You mean to call the method:
[array objectAtIndex:i];
In Objective-C, it is called "you are sending a message (objectAtIndex:i) to the array".
I am guessing, but hard to tell without your header file declarations, that your problem is you need to #import the file where your class is declared. This is the most common problem when having issues like this. It somehow does not know that it is an NSMutableArray. Also as I noted above you need to assign the value you get back from the array into a typed variable of that class so that you can then access the isChosen property.