1 tab is used for indentation
Tab, not spaces!
Declare each variable on a separate line
Avoid short or meaningless names (e.g. "a", "rbarr", "nughdeget")
Single character variable names are only okay for counters and temporaries, where the purpose of the variable is obvious
Wait when declaring a variable until it is needed
// Wrong
int a, b;
char *c, *d;
// Correct
int height;
int width;
char *nameOfThis;
char *nameOfThat;Variables and functions start with a lower-case letter. Each consecutive word in a variable’s name starts with an upper-case letter
Avoid abbreviations
// Wrong
short Cntr;
char ITEM_DELIM = '\t';
// Correct
short counter;
char itemDelimiter = '\t';Classes always start with an upper-case letter. Public classes start with a ‘Q’ (QRgb) followed by an upper case letter. Public functions most often start with a ‘q’ (qRgb). Acronyms are camel-cased (e.g. QXmlStreamReader, not QXMLStreamReader).
Use blank lines to group statements together where suited Always use only one blank line Do not use space after a keyword Always use one single space before a curly brace:
// Wrong
if (foo){
}
// Correct
if(foo) {
}For pointers or references, always use a single space between the type and ‘’ or ‘&’, but no space between the ‘’ or ‘&’ and the variable name:
// Correct
char *x;
const QString &myString;
const char * const y = "hello";Surround binary operators with spaces No space after a cast Avoid C-style casts when possible
// Wrong
char* blockOfMemory = (char*)malloc(data.size());
// Correct
char *blockOfMemory = reinterpret_cast<char *>(malloc(data.size()));Do not put multiple statements on one line By extension, use a new line for the body of a control flow statement:
// Wrong
if(foo) bar();
// Correct
if(foo)
bar();Use attached braces: The opening brace goes on the same line as the start of the statement. If the closing brace is followed by another keyword, it goes into the same line as well:
// Wrong
if(codec)
{
}
else
{
}
// Correct
if(codec) {
} else {
}Exception: Function implementations and class declarations always have the left brace on the start of a line:
// Correct
static void
foo(int g)
{
qDebug("foo: %i", g);
}
class Moo
{
};Use curly braces only when the body of a conditional statement contains more than one line:
// Wrong
if(address.isEmpty()) {
return false;
}
for(int i = 0; i < 10; ++i) {
qDebug("%i", i);
}
// Correct
if(address.isEmpty())
return false;
for(int i = 0; i < 10; ++i)
qDebug("%i", i);Exception 1: Use braces also if the parent statement covers several lines / wraps:
// Correct
if(address.isEmpty() || !isValid()
|| !codec) {
return false;
}Exception 2: Brace symmetry: Use braces also in if-then-else blocks where either the if-code or the else-code covers several lines:
// Wrong
if(address.isEmpty())
return false;
else {
qDebug("%s", qPrintable(address));
++it;
}
// Correct
if(address.isEmpty()) {
return false;
} else {
qDebug("%s", qPrintable(address));
++it;
}
// Wrong
if(a)
if(b)
...
else
...
// Correct
if(a) {
if(b)
...
else
...
}Use curly braces when the body of a conditional statement is empty
// Wrong
while(a);
// Correct
while(a) {}Use parentheses to group expressions:
// Wrong
if(a && b || c)
// Correct
if((a && b) || c)
// Wrong
a + b & c
// Correct
(a + b) & cThe case labels are in the same column as the switch Every case must have a break (or return) statement at the end or a comment to indicate that there’s intentionally no break, unless another case follows immediately.
// Correct
switch(myEnum) {
case Value1:
doSomething();
break;
case Value2:
case Value3:
doSomethingElse();
// fall through
default:
defaultHandling();
break;
}Jump statements (break, continue, return, and goto)
Do not put ‘else’ after jump statements:
// Wrong
if(thisOrThat)
return;
else
somethingElse();
// Correct
if(thisOrThat)
return;
somethingElse();Exception: If the code is inherently symmetrical, use of ‘else’ is allowed to visualize that symmetry
Keep lines shorter than 100 characters; wrap if necessary Commas go at the end of wrapped lines; operators start at the beginning of the new lines. An operator at the end of the line is easy to miss if the editor is too narrow.
// Wrong
if(longExpression +
otherLongExpression +
otherOtherLongExpression) {
}
// Correct
if(longExpression
+ otherLongExpression
+ otherOtherLongExpression) {
}When reimplementing a virtual method, do not put the virtual keyword in the header file.
On Qt5, annotate them with the Q_DECL_OVERRIDE macro after the function declaration, just before the ‘;’ (or the ‘{’ ).
Do not use both the module and class name for Qt includes.
// Correct
#include <QString>
// Wrong
#include <QtCore/QString>You can use lambdas with the following restrictions:
- You have to explicitly specify the return type (unless it's void), if the lambda contains more than a single expression.
// Correct
[]() -> QString {
Foo *foo = activeFoo();
return foo ? foo->displayName() : QString();
});
// Wrong
[]() {
Foo *foo = activeFoo();
return foo ? foo->displayName() : QString();
});- If you use static functions from the class that the lambda is located in, you have to explicitly capture this. Otherwise it does not compile with g++ 4.7 and earlier.
// Correct
void
Foo::something()
{
...
[this]() { Foo::someStaticFunction(); }
...
}
// Wrong
void
Foo::something()
{
...
[]() { Foo::someStaticFunction(); }
...
}Format the lambda according to the following rules:
- Always write parentheses for the parameter list, even if the function does not take parameters.
// Correct
[]() { doSomething(); }
// Wrong
[] { doSomething(); }- Place the capture-list, parameter list, return type, and opening brace on the first line, the body indented on the following lines, and the closing brace on a new line.
// Correct
[]() -> bool {
something();
return isSomethingElse();
}
// Wrong
[]() -> bool { something();
somethingElse(); }- Place a closing parenthesis and semicolon of an enclosing function call on the same line as the closing brace of the lambda.
// Correct
foo([]() {
something();
});- If you are using a lambda in an 'if' statement, start the lambda on a new line, to avoid confusion between the opening brace for the lambda and the opening brace for the 'if' statement.
// Correct
if(anyOf(fooList,
[](Foo foo) {
return foo.isGreat();
}) {
return;
}
// Correct - place the lambda completely on one line if it fits
if(foo([]() { return true; })) {
...
}
// Wrong
if(anyOf(fooList, [](Foo foo) {
return foo.isGreat();
}) {
return;
}You can use the auto keyword in the following cases. If in doubt (e.g. using auto could make the code less readable) do not use auto. Keep in mind that code is read much more often than written.
- When it avoids repetition of a type in the same statement.
// Correct
auto something = new MyCustomType;
auto keyEvent = static_cast<QKeyEvent *>(event);- When assigning iterator types.
// Correct
auto it = myList.const_iterator();You should prefer initializer lists over adding the entries at runtime.
// Wrong
auto myList = QStringList() << QLatin1String("FooThing") << QLatin1String("BarThing");
// Correct
QStringList myList{QStringLiteral("FooThing"), QStringLiteral("BarThing")};
QStringList myListWithSingleEntry{QStringLiteral("FooThing")};When strictly following a rule makes your code look bad, feel free to break it