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Alias std.traits.getSymbolsByUDA
Parameters
Name | Description |
---|---|
symbol | The aggregate type or module to search |
attribute | The user-defined attribute to search for |
Returns
All symbols within symbol
that have the given UDA attribute
.
Note
This is not recursive; it will not search for symbols within symbols such as nested structs or unions.
Example
enum Attr;
struct A
{
@Attr int a;
int b;
}
static assert(getSymbolsByUDA!(A, Attr) .length == 1);
static assert(hasUDA!(getSymbolsByUDA!(A, Attr)[0], Attr));
Example
enum Attr;
static struct A
{
@Attr int a;
int b;
@Attr void doStuff() {}
void doOtherStuff() {}
static struct Inner
{
// Not found by getSymbolsByUDA
@Attr int c;
}
}
// Finds both variables and functions with the attribute, but
// doesn't include the variables and functions without it.
static assert(getSymbolsByUDA!(A, Attr) .length == 2);
// Can access attributes on the symbols returned by getSymbolsByUDA.
static assert(hasUDA!(getSymbolsByUDA!(A, Attr)[0], Attr));
static assert(hasUDA!(getSymbolsByUDA!(A, Attr)[1], Attr));
Example
Finds multiple attributes
static struct UDA { string name; }
static struct B
{
@UDA("X")
int x;
@UDA("Y")
int y;
@(100)
int z;
}
// Finds both UDA attributes.
static assert(getSymbolsByUDA!(B, UDA) .length == 2);
// Finds one `100` attribute.
static assert(getSymbolsByUDA!(B, 100) .length == 1);
// Can get the value of the UDA from the return value
static assert(getUDAs!(getSymbolsByUDA!(B, UDA)[0], UDA)[0] .name == "X");
Example
Checks for UDAs on the aggregate symbol itself
static struct UDA { string name; }
@UDA("A")
static struct C
{
@UDA("B")
int d;
}
static assert(getSymbolsByUDA!(C, UDA) .length == 2);
static assert(getSymbolsByUDA!(C, UDA)[0] .stringof == "C");
static assert(getSymbolsByUDA!(C, UDA)[1] .stringof == "d");
Example
Finds nothing if there is no member with specific UDA
static struct UDA { string name; }
static struct D
{
int x;
}
static assert(getSymbolsByUDA!(D, UDA) .length == 0);
Authors
Walter Bright,
Tomasz Stachowiak (isExpressions
),
Andrei Alexandrescu,
Shin Fujishiro,
Robert Clipsham,
David Nadlinger,
Kenji Hara,
Shoichi Kato
License
Copyright © 1999-2022 by the D Language Foundation | Page generated by ddox.