Tag.getTagAttribute

Lookup a child tag and attribute by name, and retrieve a value of type T from it. Returns a default value if not found.

Useful if you only expect one attribute of type T from given the tag and attribute names. Only looks for immediate child tags of this, doesn't search recursively.

This is a shortcut for getTag().getAttribute(), except if the tag isn't found, then instead of a null reference error, it will return the requested defaultValue (or T.init by default).

class Tag

getTagAttribute

(

)

(

string fullTagName

string fullAttributeName

T defaultValue = T.init

)

if (

isValueType!T

)

Examples

import std.exception;
import sdlang.parser;

auto root = parseSource(`
	foo X=1 X="a" X=2 X="b"
	foo X=3 X="c" X=4 X="d"  // getTagAttribute considers this to override the first foo

	bar X="hi"
	bar X=379  // getTagAttribute considers this to override the first bar
`);
assert( root.getTagAttribute!int("foo", "X") == 3 );
assert( root.getTagAttribute!string("foo", "X") == "c" );

// Value found, default value ignored.
assert( root.getTagAttribute!int("foo", "X", 999) == 3 );

// Tag not found
// If you'd prefer an exception, use `expectTagAttribute` instead of `getTagAttribute`
assert( root.getTagAttribute!int("doesnt-exist", "X", 999)   == 999 );
assert( root.getTagAttribute!int("doesnt-exist", "X")        == 0   );
assert( root.getTagAttribute!int("foo", "doesnt-exist", 999) == 999 );
assert( root.getTagAttribute!int("foo", "doesnt-exist")      == 0   );

// The last "bar" tag doesn't have a string (only the first "bar" tag does)
assert( root.getTagAttribute!string("bar", "X", "Default") == "Default" );
assert( root.getTagAttribute!string("bar", "X") is null );


// Using namespaces:
root = parseSource(`
	ns1:foo X=1 X="a" X=2 X="b"
	ns1:foo X=3 X="c" X=4 X="d"
	ns2:foo X=11 X="aa" X=22 X="bb"
	ns2:foo X=33 X="cc" X=44 X="dd"

	ns1:bar attrNS:X="hi"
	ns1:bar attrNS:X=379  // getTagAttribute considers this to override the first bar
`);
assert( root.getTagAttribute!int("ns1:foo", "X") == 3  );
assert( root.getTagAttribute!int("*:foo",   "X") == 33 ); // Search all namespaces

assert( root.getTagAttribute!string("ns1:foo", "X") == "c"  );
assert( root.getTagAttribute!string("*:foo",   "X") == "cc" ); // Search all namespaces

// bar's attribute X is't in the default namespace
assert( root.getTagAttribute!int("*:bar", "X", 999) == 999 );
assert( root.getTagAttribute!int("*:bar", "X") == 0 );

// The last "bar" tag's "attrNS:X" attribute doesn't have a string (only the first "bar" tag does)
assert( root.getTagAttribute!string("*:bar", "attrNS:X", "Default") == "Default" );
assert( root.getTagAttribute!string("*:bar", "attrNS:X") is null);

Tag.getTagAttribute

Examples

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