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How do I make the method return type generic?
...nimal> T callFriend(String name, Class<T> type) {
return type.cast(friends.get(name));
}
Then call it as such:
jerry.callFriend("spike", Dog.class).bark();
jerry.callFriend("quacker", Duck.class).quack();
This code has the benefit of not generating any compiler warnings. Of course ...
How can I output the value of an enum class in C++11
...ts integer value. You need to explicitly convert it to an integer using a cast:
std::cout << static_cast<std::underlying_type<A>::type>(a) << std::endl;
You may want to encapsulate the logic into a function template:
template <typename Enumeration>
auto as_integer(...
Why unsigned integer is not available in PostgreSQL?
...< 65536);
Here is what psql gives when I try to abuse the type.
DS1=# select (346346 :: uint2);
ERROR: value for domain uint2 violates check constraint "uint2_check"
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How to avoid the “divide by zero” error in SQL?
...rder to avoid a "Division by zero" error we have programmed it like this:
Select Case when divisor=0 then null
Else dividend / divisor
End ,,,
But here is a much nicer way of doing it:
Select dividend / NULLIF(divisor, 0) ...
Now the only problem is to remember the NullIf bit, if I use the "/"...
How can I convert a std::string to int?
...stinguish between bad input (see here).
4. Fourth option: Boost's lexical_cast
#include <boost/lexical_cast.hpp>
#include <string>
std::string str;
try {
int i = boost::lexical_cast<int>( str.c_str());
float f = boost::lexical_cas...
SQL WHERE.. IN clause multiple columns
...a derived table from the subquery, and join table1 to this derived table:
select * from table1 LEFT JOIN
(
Select CM_PLAN_ID, Individual_ID
From CRM_VCM_CURRENT_LEAD_STATUS
Where Lead_Key = :_Lead_Key
) table2
ON
table1.CM_PLAN_ID=table2.CM_PLAN_ID
AND table1.Individual=table2.Indi...
C++ equivalent of java's instanceof
...
Try using:
if(NewType* v = dynamic_cast<NewType*>(old)) {
// old was safely casted to NewType
v->doSomething();
}
This requires your compiler to have rtti support enabled.
EDIT:
I've had some good comments on this answer!
Every time you need...
Select TreeView Node on right click before displaying ContextMenu
I would like to select a WPF TreeView Node on right click, right before the ContextMenu displayed.
11 Answers
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How to make a select with array contains value clause in psql
...
Try
SELECT * FROM table WHERE arr @> ARRAY['s']::varchar[]
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How to loop through all enum values in C#? [duplicate]
...Foos));
Or the typed version:
var values = Enum.GetValues(typeof(Foos)).Cast<Foos>();
I long ago added a helper function to my private library for just such an occasion:
public static class EnumUtil {
public static IEnumerable<T> GetValues<T>() {
return Enum.GetVa...