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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 19 hours ago
RhymeRhyme
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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 19 hours ago
RhymeRhyme
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
2
You can use a lambda expression that calls your actual function
– Liran Funaro
19 hours ago
1
Where do the class instance and the two parameters come from?
– Bergi
15 hours ago
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
14 hours ago
Note that a interface with a single method is roughly equivalent to astd::functiontype.
– Caleth
14 hours ago
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 19 hours ago
RhymeRhyme
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
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 19 hours ago
RhymeRhyme
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 19 hours ago
RhymeRhyme
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
edited 9 hours ago
Rhyme
asked 19 hours ago
RhymeRhyme
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
asked 19 hours ago
RhymeRhyme
565
asked 19 hours ago
RhymeRhyme
565
565
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
New contributor
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
Rhyme is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.
2
You can use a lambda expression that calls your actual function
– Liran Funaro
19 hours ago
1
Where do the class instance and the two parameters come from?
– Bergi
15 hours ago
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
14 hours ago
Note that a interface with a single method is roughly equivalent to astd::functiontype.
– Caleth
14 hours ago
add a comment |
2
You can use a lambda expression that calls your actual function
– Liran Funaro
19 hours ago
1
Where do the class instance and the two parameters come from?
– Bergi
15 hours ago
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
14 hours ago
Note that a interface with a single method is roughly equivalent to astd::functiontype.
– Caleth
14 hours ago
2
2
You can use a lambda expression that calls your actual function
– Liran Funaro
19 hours ago
You can use a lambda expression that calls your actual function
– Liran Funaro
19 hours ago
1
1
Where do the class instance and the two parameters come from?
– Bergi
15 hours ago
Where do the class instance and the two parameters come from?
– Bergi
15 hours ago
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
14 hours ago
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
14 hours ago
Note that a interface with a single method is roughly equivalent to a
std::function type.– Caleth
14 hours ago
Note that a interface with a single method is roughly equivalent to a
std::function type.– Caleth
14 hours ago
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 19 hours ago
Petar VelevPetar Velev
1,671619
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 14 hours ago
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 19 hours ago
Petar VelevPetar Velev
1,671619
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 19 hours ago
Petar VelevPetar Velev
1,671619
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 19 hours ago
Petar VelevPetar Velev
1,671619
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 19 hours ago
Petar VelevPetar Velev
1,671619
answered 19 hours ago
Petar VelevPetar Velev
1,671619
answered 19 hours ago
Petar VelevPetar Velev
1,671619
answered 19 hours ago
Petar VelevPetar Velev
1,671619
1,671619
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 14 hours ago
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 14 hours ago
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 14 hours ago
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 14 hours ago
Kate GregoryKate Gregory
17.5k74881
answered 14 hours ago
Kate GregoryKate Gregory
17.5k74881
answered 14 hours ago
Kate GregoryKate Gregory
17.5k74881
answered 14 hours ago
Kate GregoryKate Gregory
17.5k74881
17.5k74881
add a comment |
add a comment |
Rhyme is a new contributor. Be nice, and check out our Code of Conduct.
Rhyme is a new contributor. Be nice, and check out our Code of Conduct.
Rhyme is a new contributor. Be nice, and check out our Code of Conduct.
Rhyme is a new contributor. Be nice, and check out our Code of Conduct.
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2
You can use a lambda expression that calls your actual function
– Liran Funaro
19 hours ago
1
Where do the class instance and the two parameters come from?
– Bergi
15 hours ago
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
14 hours ago
Note that a interface with a single method is roughly equivalent to a
std::functiontype.– Caleth
14 hours ago