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Is storing any type of function in one variable possible?
What are the differences between a pointer variable and a reference variable in C++?What's the difference between a method and a function?What is the naming convention in Python for variable and function names?var functionName = function() vs function functionName() What is the scope of variables in JavaScript?How do you check if a variable is an array in JavaScript?Set a default parameter value for a JavaScript functionHow to determine if variable is 'undefined' or 'null'?How to check if a variable is set in Bash?JavaScript check if variable exists (is defined/initialized)
I'm trying to make a menu array where each element is a struct that stores variables for text, key that needs to be pressed to select that item and function called on that key press (something like "Quit", 'Q', Quit()). I thought this would make things more efficient, but I can't find a way to make it work with varied function and parameter types (for example one item should be able to call a void function with no parameters, another a class int function with two parameters and so on). Is there a good way to do this or am I better off giving up on the idea?
Edit: Thank you all for your advice! The proposed solutions feel a little too complex for my newbie self, but attempting to understand them gave me some ideas! I ended up making the third variable hold an enum instead of a direct function call and then created a switch function that calls other functions based on that value.
c++ function variables
asked Mar 19 at 9:51
RhymeRhyme
565
add a comment |
I'm trying to make a menu array where each element is a struct that stores variables for text, key that needs to be pressed to select that item and function called on that key press (something like "Quit", 'Q', Quit()). I thought this would make things more efficient, but I can't find a way to make it work with varied function and parameter types (for example one item should be able to call a void function with no parameters, another a class int function with two parameters and so on). Is there a good way to do this or am I better off giving up on the idea?
Edit: Thank you all for your advice! The proposed solutions feel a little too complex for my newbie self, but attempting to understand them gave me some ideas! I ended up making the third variable hold an enum instead of a direct function call and then created a switch function that calls other functions based on that value.
c++ function variables
asked Mar 19 at 9:51
RhymeRhyme
565
2
You can use a lambda expression that calls your actual function
– Liran Funaro
Mar 19 at 9:55
1
Where do the class instance and the two parameters come from?
– Bergi
Mar 19 at 13:54
3
Look up the Command pattern. Note that I’m not saying not to use a function for this. But this pattern is the generalised form of what you need.
– Konrad Rudolph
Mar 19 at 14:32
Note that a interface with a single method is roughly equivalent to astd::functiontype.
– Caleth
Mar 19 at 14:55
add a comment |
I'm trying to make a menu array where each element is a struct that stores variables for text, key that needs to be pressed to select that item and function called on that key press (something like "Quit", 'Q', Quit()). I thought this would make things more efficient, but I can't find a way to make it work with varied function and parameter types (for example one item should be able to call a void function with no parameters, another a class int function with two parameters and so on). Is there a good way to do this or am I better off giving up on the idea?
Edit: Thank you all for your advice! The proposed solutions feel a little too complex for my newbie self, but attempting to understand them gave me some ideas! I ended up making the third variable hold an enum instead of a direct function call and then created a switch function that calls other functions based on that value.
c++ function variables
asked Mar 19 at 9:51
RhymeRhyme
565
I'm trying to make a menu array where each element is a struct that stores variables for text, key that needs to be pressed to select that item and function called on that key press (something like "Quit", 'Q', Quit()). I thought this would make things more efficient, but I can't find a way to make it work with varied function and parameter types (for example one item should be able to call a void function with no parameters, another a class int function with two parameters and so on). Is there a good way to do this or am I better off giving up on the idea?
Edit: Thank you all for your advice! The proposed solutions feel a little too complex for my newbie self, but attempting to understand them gave me some ideas! I ended up making the third variable hold an enum instead of a direct function call and then created a switch function that calls other functions based on that value.
c++ function variables
c++ function variables
asked Mar 19 at 9:51
RhymeRhyme
565
asked Mar 19 at 9:51
RhymeRhyme
565
edited Mar 19 at 20:03
Rhyme
asked Mar 19 at 9:51
RhymeRhyme
565
asked Mar 19 at 9:51
RhymeRhyme
565
asked Mar 19 at 9:51
RhymeRhyme
565
565
2
You can use a lambda expression that calls your actual function
– Liran Funaro
Mar 19 at 9:55
1
Where do the class instance and the two parameters come from?
– Bergi
Mar 19 at 13:54
3
Look up the Command pattern. Note that I’m not saying not to use a function for this. But this pattern is the generalised form of what you need.
– Konrad Rudolph
Mar 19 at 14:32
Note that a interface with a single method is roughly equivalent to astd::functiontype.
– Caleth
Mar 19 at 14:55
add a comment |
2
You can use a lambda expression that calls your actual function
– Liran Funaro
Mar 19 at 9:55
1
Where do the class instance and the two parameters come from?
– Bergi
Mar 19 at 13:54
3
Look up the Command pattern. Note that I’m not saying not to use a function for this. But this pattern is the generalised form of what you need.
– Konrad Rudolph
Mar 19 at 14:32
Note that a interface with a single method is roughly equivalent to astd::functiontype.
– Caleth
Mar 19 at 14:55
2
2
You can use a lambda expression that calls your actual function
– Liran Funaro
Mar 19 at 9:55
You can use a lambda expression that calls your actual function
– Liran Funaro
Mar 19 at 9:55
1
1
Where do the class instance and the two parameters come from?
– Bergi
Mar 19 at 13:54
Where do the class instance and the two parameters come from?
– Bergi
Mar 19 at 13:54
3
3
Look up the Command pattern. Note that I’m not saying not to use a function for this. But this pattern is the generalised form of what you need.
– Konrad Rudolph
Mar 19 at 14:32
Look up the Command pattern. Note that I’m not saying not to use a function for this. But this pattern is the generalised form of what you need.
– Konrad Rudolph
Mar 19 at 14:32
Note that a interface with a single method is roughly equivalent to a
std::function type.– Caleth
Mar 19 at 14:55
Note that a interface with a single method is roughly equivalent to a
std::function type.– Caleth
Mar 19 at 14:55
add a comment |
2 Answers
2
active
oldest
votes
There are actually a few ways of doing this.
One way is to use std::bind to bind all functions to void func(void) then you can store them equally.
The other way is to create a generic function/lambda which will call your function.
To store your functions you can use std::function.
Also consider overriding operator() of your classes.
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
add a comment |
The classic way of handling this is to have all the functions take the same parameters, and for those to be very flexible. For example, an integer or enum, and a pointer.
- your no-parameter function is passed -1 and
nullptrand ignores them - your multi-parameter function casts the pointer to a pointer to some struct or class that holds all the bits and pieces it needs (and of course your calling code made that instance and passed its address)
The reason an enum or integer is hoisted out as one of the parameters is that "command type" is a super popular thing to need, so why do all that casting and extracting to get it?
If you have a performance problem as a result of this approach, then there are others, but this has literally been used for decades in Windows.
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
add a comment |
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2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
There are actually a few ways of doing this.
One way is to use std::bind to bind all functions to void func(void) then you can store them equally.
The other way is to create a generic function/lambda which will call your function.
To store your functions you can use std::function.
Also consider overriding operator() of your classes.
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
add a comment |
There are actually a few ways of doing this.
One way is to use std::bind to bind all functions to void func(void) then you can store them equally.
The other way is to create a generic function/lambda which will call your function.
To store your functions you can use std::function.
Also consider overriding operator() of your classes.
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
add a comment |
There are actually a few ways of doing this.
One way is to use std::bind to bind all functions to void func(void) then you can store them equally.
The other way is to create a generic function/lambda which will call your function.
To store your functions you can use std::function.
Also consider overriding operator() of your classes.
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
There are actually a few ways of doing this.
One way is to use std::bind to bind all functions to void func(void) then you can store them equally.
The other way is to create a generic function/lambda which will call your function.
To store your functions you can use std::function.
Also consider overriding operator() of your classes.
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
answered Mar 19 at 9:58
Petar VelevPetar Velev
1,748719
1,748719
add a comment |
add a comment |
The classic way of handling this is to have all the functions take the same parameters, and for those to be very flexible. For example, an integer or enum, and a pointer.
- your no-parameter function is passed -1 and
nullptrand ignores them - your multi-parameter function casts the pointer to a pointer to some struct or class that holds all the bits and pieces it needs (and of course your calling code made that instance and passed its address)
The reason an enum or integer is hoisted out as one of the parameters is that "command type" is a super popular thing to need, so why do all that casting and extracting to get it?
If you have a performance problem as a result of this approach, then there are others, but this has literally been used for decades in Windows.
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
add a comment |
The classic way of handling this is to have all the functions take the same parameters, and for those to be very flexible. For example, an integer or enum, and a pointer.
- your no-parameter function is passed -1 and
nullptrand ignores them - your multi-parameter function casts the pointer to a pointer to some struct or class that holds all the bits and pieces it needs (and of course your calling code made that instance and passed its address)
The reason an enum or integer is hoisted out as one of the parameters is that "command type" is a super popular thing to need, so why do all that casting and extracting to get it?
If you have a performance problem as a result of this approach, then there are others, but this has literally been used for decades in Windows.
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
add a comment |
The classic way of handling this is to have all the functions take the same parameters, and for those to be very flexible. For example, an integer or enum, and a pointer.
- your no-parameter function is passed -1 and
nullptrand ignores them - your multi-parameter function casts the pointer to a pointer to some struct or class that holds all the bits and pieces it needs (and of course your calling code made that instance and passed its address)
The reason an enum or integer is hoisted out as one of the parameters is that "command type" is a super popular thing to need, so why do all that casting and extracting to get it?
If you have a performance problem as a result of this approach, then there are others, but this has literally been used for decades in Windows.
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
The classic way of handling this is to have all the functions take the same parameters, and for those to be very flexible. For example, an integer or enum, and a pointer.
- your no-parameter function is passed -1 and
nullptrand ignores them - your multi-parameter function casts the pointer to a pointer to some struct or class that holds all the bits and pieces it needs (and of course your calling code made that instance and passed its address)
The reason an enum or integer is hoisted out as one of the parameters is that "command type" is a super popular thing to need, so why do all that casting and extracting to get it?
If you have a performance problem as a result of this approach, then there are others, but this has literally been used for decades in Windows.
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
answered Mar 19 at 14:35
Kate GregoryKate Gregory
17.5k74881
17.5k74881
add a comment |
add a comment |
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2
You can use a lambda expression that calls your actual function
– Liran Funaro
Mar 19 at 9:55
1
Where do the class instance and the two parameters come from?
– Bergi
Mar 19 at 13:54
3
Look up the Command pattern. Note that I’m not saying not to use a function for this. But this pattern is the generalised form of what you need.
– Konrad Rudolph
Mar 19 at 14:32
Note that a interface with a single method is roughly equivalent to a
std::functiontype.– Caleth
Mar 19 at 14:55