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handle the nil interface better in reflect and print

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R=rsc
DELTA=25  (19 added, 0 deleted, 6 changed)
OCL=20985
CL=20985
This commit is contained in:
Rob Pike 2008-12-11 12:59:49 -08:00
parent 793a6effcf
commit ac09eb4f49
3 changed files with 25 additions and 6 deletions
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22
src/lib/fmt/print.go
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@ -307,9 +307,12 @@ func parsenum(s string, start, end int) (n int, got bool, newi int) {
}
func (p *P) printField(field reflect.Value) (was_string bool) {
if stringer, ok := field.Interface().(String); ok {
p.addstr(stringer.String());
return false; // this value is not a string
inter := field.Interface();
if inter != nil {
if stringer, ok := inter.(String); ok {
p.addstr(stringer.String());
return false; // this value is not a string
}
}
s := "";
switch field.Kind() {
@ -363,6 +366,14 @@ func (p *P) printField(field reflect.Value) (was_string bool) {
p.add('{');
p.doprint(field, true, false);
p.add('}');
case reflect.InterfaceKind:
inter := field.(reflect.InterfaceValue).Get();
if inter == nil {
s = "<nil>"
} else {
// should never happen since a non-nil interface always has a type
s = "<non-nil interface>";
}
default:
s = "?" + field.Type().String() + "?";
}
@ -421,8 +432,9 @@ func (p *P) doprintf(format string, v reflect.StructValue) {
}
field := getField(v, fieldnum);
fieldnum++;
if c != 'T' { // don't want thing to describe itself if we're asking for its type
if formatter, ok := field.Interface().(Format); ok {
inter := field.Interface();
if inter != nil && c != 'T' { // don't want thing to describe itself if we're asking for its type
if formatter, ok := inter.(Format); ok {
formatter.Format(p, c);
continue;
}