CONDITIONALLY DISABLE LINK CSS ONLY CODE
Sometimes this would lead to too much code duplication.Īn example where similar techniques have to be used are the upcoming std::optional and std::variant. (or even a completely separate type) would have solved the problem better, If you wish to enable/disable/show/hide controls based on the role this would be nothing more than 'security by obscurity' since switching off styles or setting a browser to a specific css file to override what. An administrator should link my admin.css file.
CONDITIONALLY DISABLE LINK CSS ONLY VERIFICATION
The compiler can’t generate them automatically anymore,Įven though in this example here partial template specializations Is it possible to send email verification only to some users My use case is nothing extra ordinary, some users sign-up directly and some are invited by others and if user already got invite link. I want to conditionally link a CSS file base on the users Membership role. To disable them, simply inherit from a non-copy/moveable type. So that they are automatically generated in your class. You have to write them in a separate helper class, This approach works for all member functions except for copy/move operations, You have to make the function a template first,īy adding a dummy template parameter and making the SFINAE expression somehow dependent on it. If you have a non-templated member function of a class template and you want to conditionally remove it,
So the member function will not be available. Now if AllowNull = true, the compiler can generate the move operations.īut if it is false, it can’t, because the base class is not moveable. You wouldn’t bother with the techniques here. If AllowNull is true it behaves like the regular version,īut if it is false, the pointer must not be null. Otherwise the function will be “greedy” and accept more than it should - making some traits near useless,Īs they only check for existence and the error only occurs later.Ĭonditionally removing functions if their template parameters don’t fulfill certain propertiesīut what if you have member functions of a class template that are not templates themselves?Ĭonsider a modified - and very simplified - std::unique_ptr that takes an additional parameter AllowNull. It is often beneficial if you can conditionally disable the function if the type does not have some required properties. Or anything whose existence might be queried with type traits to further constrain other functions, If the function template has a rather generic name like operator=, is a constructor, Consider that you have a function template that takes a parameter on type T.
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