scope

问题 I have a model Category that has_many Pendencies . I would like to create a scope that order the categories by the amount of Pendencies that has active = true without excluding active = false . What I have so far is: scope :order_by_pendencies, -> { left_joins(:pendencies).group(:id).order('COUNT(pendencies.id) DESC')} This will order it by number of pendencies, but I want to order by pendencies that has active = true . Another try was: scope :order_by_pendencies, -> { left_joins(:pendencies)

问题 Consider the following: def f(): a = 2 b = [a + i for i in range(3)] f() This runs without problems. As I understand it (please correct me if I'm wrong, though), the list comprehension expression introduces a new scope, but since it is created within a function (as opposed to, say, a class), it has access to the surrounding scope, including the variable a . In contrast, if I were to enter debug mode, stop at line 3 above, and then just manually write the following in the interpreter >>> b =

问题 Consider the following: def f(): a = 2 b = [a + i for i in range(3)] f() This runs without problems. As I understand it (please correct me if I'm wrong, though), the list comprehension expression introduces a new scope, but since it is created within a function (as opposed to, say, a class), it has access to the surrounding scope, including the variable a . In contrast, if I were to enter debug mode, stop at line 3 above, and then just manually write the following in the interpreter >>> b =

问题 I tried different websites but I don't get it. Could you explain it in simple english? 回答1: "scope" is a namespace of the compiler; "linkage" is about compiled units. I explain a bit more: A variable declared in a function has the scope of that function, i.e. it is visible only within that function. A variable declared as static in a source file, can be seen only by the code in that source file (and all included files!). Variables can also have global scope: they can be referred to in a

问题 I tried different websites but I don't get it. Could you explain it in simple english? 回答1: "scope" is a namespace of the compiler; "linkage" is about compiled units. I explain a bit more: A variable declared in a function has the scope of that function, i.e. it is visible only within that function. A variable declared as static in a source file, can be seen only by the code in that source file (and all included files!). Variables can also have global scope: they can be referred to in a

问题 I need to use type aliases via using (or any other method) in situations like this: template <class T> typename std::enable_if< /*HERE*/>::value f (...) {}; Where I wrote HERE there are long and more than one types defined inside structures, and instead of writing typename <very long templated struct dependent on T>::type I want to write a shortcut. And I encountered this in more situations like template specializations and suffix return type syntax. So Is there any way of using using (no pun

问题 Sourcing a file normally from another script, I can access its variables. If I source a script from within a function, its variables aren't global, which seems to contradict the manpage: FUNCTION Variables local to the function may be declared with the local builtin command. Ordinarily, variables and their values are shared between the function and its caller. source filename [arguments] Read and execute commands from filename in the current shell environment Happens with all my conveniently

问题 Sourcing a file normally from another script, I can access its variables. If I source a script from within a function, its variables aren't global, which seems to contradict the manpage: FUNCTION Variables local to the function may be declared with the local builtin command. Ordinarily, variables and their values are shared between the function and its caller. source filename [arguments] Read and execute commands from filename in the current shell environment Happens with all my conveniently

问题 Sourcing a file normally from another script, I can access its variables. If I source a script from within a function, its variables aren't global, which seems to contradict the manpage: FUNCTION Variables local to the function may be declared with the local builtin command. Ordinarily, variables and their values are shared between the function and its caller. source filename [arguments] Read and execute commands from filename in the current shell environment Happens with all my conveniently

问题 whenever I use a trailing closure on an action ... example: run(SKAction.wait(forDuration: 10)){timeRemains = false} I’m seeing this: Reference to property ( anything ) in closure requires explicitly ‘self’ to make capture semantics explicit. What does this mean? And what is it on about? I'm curious because I'm only ever doing this in the context/scope of the property or function I want to call in the trailing closure, so don't know why I need `self and fascinated by the use of the word