I was reading this example: http://blog.ondrejsv.com/post/AppSettingsReader-and-reading-typed-and-nullable-application-settings.aspx and I noticed in this line of code:
int failCount = (int) appSettingsReader.GetValue("FailAttemptCount", typeof(int));
I don't understand why there is a (int) before appSettingsReader, what it does, etc.
The call to GetValue is designed to return the result as various possible types, but the declared return value is Object. So you tell it to return an int, but then you have to cast the result to int so you can reference it as such.
it casts the returned object to an int, this makes sure that the object you get back can be assigend to the int variable failCount. This is needed since the return type of GetValue is Object, not int
Related
I am trying to perform logic based on the values of two integers. Here I am defining my integers, and I also have NSLog so I can see if the values are correct when I run the code:
int theHikeFlag = (int)[theNewHikeFlag objectAtIndex:(theID-1)];
NSLog(#"theHikeFlag: %#",theHikeFlag);
int fromTheDB = [self.detailItem hikeFlag];
NSLog(#"fromTheDB: %d",fromTheDB);
And here is the logic:
if (theHikeFlag==1) {
hikeString=#"You have";
}
else if (theHikeFlag==0) {
hikeString=#"You have not";
}
else {
if (fromTheDB==1) {
hikeString=#"You have";
}
else {
hikeString=#"You have not";
}
}
As an example of how this code is working. When theHikeFlag=1 and fromTheDB=0, the code bypasses the if and the else if and goes straight to the else and sets hikeString="You have not". This means that my result is irrelevant of theHikeFlag and is based on the fromTheDB integer.
Since you cannot store ints in an array, the line
(int)[theNewHikeFlag objectAtIndex:(theID-1)];
is not doing what you think it should. You need to pull the data from NSNumber, not cast to int.
int theHikeFlag = [[theNewHikeFlag objectAtIndex:(theID-1)] intValue];
The reason why the log output is correct is a bit funny: you made two mistakes in a row! First, you re-interpreted a pointer as an int, and then you let NSLog re-interpret it as an object again by adding a format specifier %# that is incompatible with int, but works fine with pointers! Since the int value contains a pointer to NSNumber, NSLog produces the "correct" output.
I have en error when try to cast own enumerator to address book values:
typedef enum {
kACTextFirstName = kABPersonFirstNameProperty, // error: expression is not an integer constant expression
kACTextLastName = (int)kABPersonLastNameProperty, // error: expression is not an integer constant expression
} ACFieldType;
How to solve the problem?
Thank you.
I need to init my enum using ABAddressBook's framework const values such as kABPersonLastNameProperty or kABPersonFirstNameProperty.
In C (unlike in C++), an object declared const, even if it's initialized with a constant expression, cannot be used as a constant.
You didn't bother to show us the declaration of kABPersonFirstNameProperty, but I"m guessing it's declared something like:
const int kABPersonFirstNameProperty = 42;
If you need to use the name kABPersonFirstNameProperty as a constant expression, you can either declare it as a macro:
#define kABPersonFirstNameProperty 42
or as an enumeration constant:
enum { kABPersonFirstNameProperty = 42 };
Note that the enum hack only lets you declare constants of type int.
Likewise for kABPersonLastNameProperty.
(And why do you cast one of them to int, but not the other?)
If that doesn't answer your question, it's because you didn't give us enough information.
I have an array of type int. It has one place and I want to copy that to a variable of type int.
Ex:
Random randomNum = new Random();
int myNumber = randomNum.Next(1,1000);
int[] puterNumber = new int[1];
puterNumber[ 1 ] = myNumber;
Later in my code..
int myPuterNumber;
myPuterNumber = puterNumber[ 1 ];
I get a message on mouseover saying 'Cannot resolve symbol 'puterNumber' '
Am I missing a step for copying the value of the array to an int variable?
This looks like a scope error, probably due to object structure if you are using Java. Honestly more code would help make it clear where exactly the problem was originating from.
enum {
ValidationLoginFailed=2000,
ValidationSessionTokenExpired=2001,
ValidationSessionTokenInvalid=2002,
ValidationEmailNotFound=2003
ValidationSucccesMIN=ValidationLoginFailed,
ValidationSucccesMAX=ValidationEmailNotFound,
ValdationValidSuccessCode=9999,
ValdationInvalidCode=10000
};
typedef int ValidationStatusCodes;
please help me out.
In your code, ValidationStatusCodes means int, not your anonymous enum type. So they aren't actually connected in any way.
However, since your enum contains int values, you could say that there's some sort of relation. You can pass the names of the enumerated values and they will be considered of the int or ValidationStatusCodes type.
By the way, Apple does something similar to what you do, except they typedef their collective names to NSInteger or NSUInteger instead of int or uint. See this question for an example.
With all that said, a more common practice is to typedef your custom type name directly to the anonymous enum, like this:
typedef enum {
ValidationLoginFailed = 2000,
ValidationSessionTokenExpired = 2001,
ValidationSessionTokenInvalid = 2002,
ValidationEmailNotFound = 2003
ValidationSuccessMIN = ValidationLoginFailed,
ValidationSuccessMAX = ValidationEmailNotFound,
ValdationValidSuccessCode = 9999,
ValdationInvalidCode = 10000
} ValidationStatusCodes;
if the variable in object_getIvar is a basic data type (eg. float, int, bool) how do I get the value as the function returns a pointer (id) according to the documentation. I've tried casting to an int, int* but when I try to get that to NSLog, I get error about an incompatible pointer type.
Getting:
myFloat = 2.34f;
float myFloatValue;
object_getInstanceVariable(self, "myFloat", (void*)&myFloatValue);
NSLog(#"%f", myFloatValue);
Outputs:
2.340000
Setting:
float newValue = 2.34f;
unsigned int addr = (unsigned int)&newValue;
object_setInstanceVariable(self, "myFloat", *(float**)addr);
NSLog(#"%f", myFloat);
Outputs:
2.340000
For ARC:
Inspired by this answer: object_getIvar fails to read the value of BOOL iVar.
You have to cast function call for object_getIvar to get basic-type ivars.
typedef int (*XYIntGetVariableFunction)(id object, const char* variableName);
XYIntGetVariableFunction intVariableFunction = (XYIntGetVariableFunction)object_getIvar;
int result = intVariableFunction(object, intVarName);
I have made a small useful macro for fast definition of such function pointers:
#define GET_IVAR_OF_TYPE_DEFININTION(type, capitalized_type) \
typedef type (*XY ## capitalized_type ## GetVariableFunctionType)(id object, Ivar ivar); \
XY ## capitalized_type ## GetVariableFunctionType XY ## capitalized_type ## GetVariableFunction = (XY ## capitalized_type ## GetVariableFunctionType)object_getIvar;
Then, for basic types you need to specify calls to macro (params e.g. (long long, LongLong) will fit):
GET_IVAR_OF_TYPE_DEFININTION(int, Int)
And after that a function for receiving int(or specified) variable type become available:
int result = XYIntGetVariableFunction(object, variableName)
The value that is returned is the value from the right place in the object; just not the right type. For int and BOOL (but not float), you could just cast the pointer to an int or BOOL, since pointers and ints are the same size and they can be cast to each other:
(int)object_getIvar(obj, myIntVar)
It's probably boxing the value in an NSNumber. You can verify this by NSLogging the returned id's className, like so:
id returnedValue = object_getIvar(self, myIntVar);
NSLog(#"Class: %#", [returnedValue className]);
Edit: I found another question just like this one here: Handling the return value of object_getIvar(id object, Ivar ivar)
From my own experimentation, it would appear that my original assumption was incorrect. int and float and other primitives appear to be returned as the actual value. However, it would be appropriate to use ivar_getTypeEncoding to verify that the returned value is the type that you're expecting it to be.
you can use object_getInstanceVariable directly: (haven't tested it)
void *ptr_to_result;
object_getInstanceVariable(obj, "intvarname", &ptr_to_result);
float result = *(float *)ptr_to_result;