arg 的这种用法可以吗?
Is this usage of arg ok?
msg.append(QString("\"settime\": %1000,") .arg(eventList[i].failureBegin)); // set time
我想知道 %1 紧挨着 000 是否可以。因为只有 1 个参数,所以显然 QString 不会混淆,但是如果我有 10 个 .arg() 那么它会将它与 %10 混淆,对吗?是否有一个转义序列,或者我是否必须将其分解为串联?
不行。您可以探索 source code of QString::arg 或让我向您展示。
QString QString::arg(qlonglong a, int fieldWidth, int base, QChar fillChar) const
{
ArgEscapeData d = findArgEscapes(*this);
if (d.occurrences == 0) {
qWarning() << ""QString::arg: Argument missing:"" << *this << ',' << a;
return *this;
}
//.... something not important.
}
这就是findArgEscapes
的实现方式。我认为 Qt 的源代码比大多数 STL 实现更具可读性。
static ArgEscapeData findArgEscapes(const QString &s)
{
const QChar *uc_begin = s.unicode();
const QChar *uc_end = uc_begin + s.length();
ArgEscapeData d;
d.min_escape = INT_MAX;
d.occurrences = 0;
d.escape_len = 0;
d.locale_occurrences = 0;
const QChar *c = uc_begin;
while (c != uc_end) {
while (c != uc_end && c->unicode() != '%')
++c;
if (c == uc_end)
break;
const QChar *escape_start = c;
if (++c == uc_end)
break;
bool locale_arg = false;
if (c->unicode() == 'L') {
locale_arg = true;
if (++c == uc_end)
break;
}
int escape = c->digitValue();
if (escape == -1)
continue;
++c;
if (c != uc_end) {
int next_escape = c->digitValue();
if (next_escape != -1) {
escape = (10 * escape) + next_escape; //*************
++c;
}
}
if (escape > d.min_escape)
continue;
if (escape < d.min_escape) {
d.min_escape = escape;
d.occurrences = 0;
d.escape_len = 0;
d.locale_occurrences = 0;
}
++d.occurrences;
if (locale_arg)
++d.locale_occurrences;
d.escape_len += c - escape_start;
}
return d;
}
msg.append(QString("\"settime\": %1000,") .arg(eventList[i].failureBegin)); // set time
我想知道 %1 紧挨着 000 是否可以。因为只有 1 个参数,所以显然 QString 不会混淆,但是如果我有 10 个 .arg() 那么它会将它与 %10 混淆,对吗?是否有一个转义序列,或者我是否必须将其分解为串联?
不行。您可以探索 source code of QString::arg 或让我向您展示。
QString QString::arg(qlonglong a, int fieldWidth, int base, QChar fillChar) const
{
ArgEscapeData d = findArgEscapes(*this);
if (d.occurrences == 0) {
qWarning() << ""QString::arg: Argument missing:"" << *this << ',' << a;
return *this;
}
//.... something not important.
}
这就是findArgEscapes
的实现方式。我认为 Qt 的源代码比大多数 STL 实现更具可读性。
static ArgEscapeData findArgEscapes(const QString &s)
{
const QChar *uc_begin = s.unicode();
const QChar *uc_end = uc_begin + s.length();
ArgEscapeData d;
d.min_escape = INT_MAX;
d.occurrences = 0;
d.escape_len = 0;
d.locale_occurrences = 0;
const QChar *c = uc_begin;
while (c != uc_end) {
while (c != uc_end && c->unicode() != '%')
++c;
if (c == uc_end)
break;
const QChar *escape_start = c;
if (++c == uc_end)
break;
bool locale_arg = false;
if (c->unicode() == 'L') {
locale_arg = true;
if (++c == uc_end)
break;
}
int escape = c->digitValue();
if (escape == -1)
continue;
++c;
if (c != uc_end) {
int next_escape = c->digitValue();
if (next_escape != -1) {
escape = (10 * escape) + next_escape; //*************
++c;
}
}
if (escape > d.min_escape)
continue;
if (escape < d.min_escape) {
d.min_escape = escape;
d.occurrences = 0;
d.escape_len = 0;
d.locale_occurrences = 0;
}
++d.occurrences;
if (locale_arg)
++d.locale_occurrences;
d.escape_len += c - escape_start;
}
return d;
}