Re: Issue with traits usability

[Meta via Digitalmars-d-learn]

On Wednesday, 21 March 2018 at 15:36:01 UTC, Márcio Martins wrote:

Hi!

How do I get past this?


static struct X {
int x;
private enum T = 1;
private alias M = string;
}

foreach (Member; __traits(allMembers, X)) {
	pragma(msg, __traits(getProtection, __traits(getMember, X, 
Member)));

}


Output:

public
private
c.d(1084): Error: argument string has no protection
c.d(1084):while evaluating pragma(msg, 
__traits(getProtection, string))



What I want to achieve essentially is skip all X's aliases and 
templates, but get everything else, like enums and data 
members. How would I go about this in a robust way?

I actually want to skip aliases, and templates.


In addition to Simen's answer, you can you 
std.traits.FieldNameTuple to get only the fields of your struct 
(which only includes struct members that are actually part of the 
struct's memory layout):


import std.traits;

static struct X {
int x;
private enum T = 1;
private alias M = string;
}

void main()
{
foreach (Member; FieldNameTuple!X) {
pragma(msg, __traits(getProtection, __traits(getMember, 
X, Member)));

}
}

This example prints "public" once.

Re: Issue with traits usability

[Simen Kjærås via Digitalmars-d-learn]

On Wednesday, 21 March 2018 at 15:36:01 UTC, Márcio Martins wrote:

Hi!

How do I get past this?


static struct X {
int x;
private enum T = 1;
private alias M = string;
}

foreach (Member; __traits(allMembers, X)) {
	pragma(msg, __traits(getProtection, __traits(getMember, X, 
Member)));

}


Output:

public
private
c.d(1084): Error: argument string has no protection
c.d(1084):while evaluating pragma(msg, 
__traits(getProtection, string))



What I want to achieve essentially is skip all X's aliases and 
templates, but get everything else, like enums and data 
members. How would I go about this in a robust way?

I actually want to skip aliases, and templates.



__traits(compiles) is your friend:

unittest {
static struct X {
int x;
private enum T = 1;
private alias M = string;
}

foreach (Member; __traits(allMembers, X)) {
static if (__traits(compiles, __traits(getProtection, 
__traits(getMember, X, Member {
pragma(msg, __traits(getProtection, 
__traits(getMember, X, Member)));

}
}
}

--
  Simen

Issue with traits usability

[Márcio Martins via Digitalmars-d-learn]

Hi!

How do I get past this?


static struct X {
int x;
private enum T = 1;
private alias M = string;
}

foreach (Member; __traits(allMembers, X)) {
	pragma(msg, __traits(getProtection, __traits(getMember, X, 
Member)));

}


Output:

public
private
c.d(1084): Error: argument string has no protection
c.d(1084):while evaluating pragma(msg, 
__traits(getProtection, string))



What I want to achieve essentially is skip all X's aliases and 
templates, but get everything else, like enums and data members. 
How would I go about this in a robust way?

I actually want to skip aliases, and templates.