I'd like to test the value of an enumeration attribute of a DOORs object. How can this be done? And where can I find a DXL documentation describing basic features like this?
if (o."Progress" == 0) // This does NOT work
{
// do something
}
So after two weeks and an expired bounty I finally made it.
Enum-Attributes can be assigned to int or string variables as desired. But you have to assign to a variable to perform such a conversion. It is not casted when a mere comparison is done like in my example. So here comes the solution:
int tmp = o."Progress"
if (tmp == 0)
{
// do something
}
When tmp is a string, a comparison to the enum literals is possible.
That was easy. Wasn't it? And here I finally found the everything-you-need-to-know-about-DXL manual.
For multi-valued enumerations, the best way is if (isMember(o."Progress", "0")) {. The possible enumerations for single and multi-enumeration variables are considered strings, so Steve's solution is the best dxl way for the single enumeration.
You can also do
if(o."Progress" "" == "0")
{
//do something
}
This will cast the attribute value to a string and compare it to the string "0"
If you're talking about the "related number" that is assignable from the Edit Types box, then you'll need to start by getting the position of the enumeration string within the enum and then retrieve EnumName[k].value .
I'm no expert at DXL, so the only way to find the index that I know of off the top of my head is to loop over 1 : EnumName.size and when you get a match to the enumeration string, use that loop index value to retrieve the enumeration "related number."
Related
As mentioned in Go specification:
"A type determines a set of values together with operations and methods specific to those values."
To introduce an operation or method to be applied on the values of a type,
Is that operation applied on values (taken from a set) supposed to give the result (or value) from the same set?
For example, in the below code, findName() is not supposed to be a method on type user. Instead findName() should be a helper function.
type user struct {
name string
email string
age int
}
func (u user) findElder(other user) user {
if u.age >= other.age {
return u
}
return other
}
func (u user) findName() string {
return u.name
}
"operations and methods specific to those values" does not mean that they are unique to those values, or that they result in those values.
According to Google, "specific" means "clearly defined or identified." In this quote from the Go spec, the word "specific" is used with regard to the fact that Go is strongly typed, meaning that operations and methods work on the types that they are defined or identified to work on.
For example, the == operator is specified to work on integer types, thus, the == operator is specific to values of int, int32, uint8, etc.
No, I don't think that the operation applied on values (taken from a set) are supposed to give the result (or value), only from the same set. They can be from a different set of values as well. It all depends on the use case, the design of the type and the operation.
So in your case, findName() can very well be a method even though it is returning something not in the set of input values.
I have seen when coding in LINQ that when a value is assigned to a field sometimes is in this way Table["Field"] and any others like this Table.Field but can somebody explain me what's the difference please?
For example when modifying a field:
var ttAbccode_xRow =
(from ttAbccode_Row in ds.ABCCode select ttAbccode_Row).FirstOrDefault();
if (ttAbccode_xRow != null) {
ttAbccode_xRow["PI"] = 3.1416;
}
or
if (ttAbccode_xRow != null) {
ttAbccode_xRow.PI = 3.1416;
}
Accessing field via indexer (square brackets) returns object data type. That means that your compiler cannot detect data types incompatibility. You could assing for example string value (eg. "abcd") and you won't get error at design time, but as late as at runtime.
Second method (if available in your result set) is much more safe. Your property will have proper data type hence compiler will detect data types incompatibility at design time.
If I had both access methods available I would always prefer second one. It is less error prone.
I have a method drive that goes like this:
public double drive(double milesTraveled, double gasUsed)
{
gasInTank -= gasUsed;
return totalMiles += milesTraveled;
}
I know I can't return multiple values from a method, but that's kind of what I need to do because I need both of these values in my main method, and as it is now it's obviously only returning the one. I can't think of anything that would work. Sorry if this is a super beginner question. What can I do to get both values to return from the method?
You can return multiple value from a function. To do this You can use structure.
In the structure you can keep required field and can return structure variable after operation.
You can also make a class for the required field if You are using OOPS supporting language but Structure is best way.
In most languages you can only return a single value from a method. That single value could be a complex type, such as a struct, array or object.
Some languages also allow you to define output parameters or pass in pointers or references to outside storage locations. These kinds of parameters also allow you to return additional values from your method.
not sure, but can you take array of your values?
array[0]=gasInTank;
array[0] -= gasUsed;
array[1]=milesTraveled;
array[1] -= milesTraveled;
return array;
I've seen classes where constants are passed to methods, I guess its done to define some kind of setting in that function. I cant find it anywhere now to try to find out the logic, so I though I could ask here. How and why do you use this concept and where can I find more information about it?
The example below is written in PHP, but any language that handles constants would do I guess..
// Declaring class
class ExampleClass{
const EXAMPLE_CONST_1 = 0;
const EXAMPLE_CONST_2 = 1;
function example_method($constant(?)){
if($constant == ExampleClass::EXAMPLE_CONST_1)
// do this
else if($constant == ExampleClass::EXAMPLE_CONST_2)
// do that
}
}
// Using class
$inst = new ExampleClass();
$inst->example_method(ExampleClass::EXAMPLE_CONST_1);
To me its more clear to pass "ExampleClass::EXAMPLE_CONST_1" than to just pass "1", but it's that the only reason to pass constant?
Simply passing 1 doesn't say much. By having a constant you can have a description about the settings in the name.
example:
constant RAIN = 1;
method setWeather(RAIN);
Atleast that's how and why I use it.
It is always a good idea to avoid literals being passed around. By assigning a name, anyone reading your code has a chance to understand what that value means - a number has no meaning. It might also help you maintaining your code: If for some requirement the value has to be changed, you can easily do it in one place, instead of checking each and every value occurrence.
I have a list with objects of x type. Those objects have an attribute name.
I want to find if a string matchs any of those object names. If I would have a list with the object names I just would do if string in list, so I was wondering given the current situation if there is a way to do it without having to loop over the list.
any(obj for obj in objs if obj.name==name)
Note, that it will stop looping after first match found.
Here's another
dict( (o.name,o) for o in obj_list )[name]
The trick, though, is avoid creating a list obj_list in the first place.
Since you know that you're going to fetch objects by the string value of an attribute, do not use a list, use a dictionary instead of a list.
A dictionary can be trivially "searched" for matching strings. It's a better choice than a list.
What do you want to do if the string matches? Do you just want to return True/False, or return a list of objects that match?
To return a boolean:
any(obj.name == name for obj in objs)
(I find this slightly more readable than Denis Otkidach's version).
to filter the list:
[obj for obj in objs if obj.name == name]
if string in [x.name for x in list_of_x]
for i in listOfItemsOfTypeX:
if i.name == myString: return True
return False