Qt Coding Style

This is a overview of the coding convention we use when writing Qt code.
The data has been gathered by mining the Qt sources, discussion forums,
email threads and through collaboration of the developers.

Indentation

4 spaces are used for indentation

Spaces, not tabs!

Declaring variables

Declare each variable on a separate line

Avoid short (e.g., a,rbarr,nughdeget) names whenever possible

Single character variable names are only okay for counters and temporaries, where the purpose of the variable is obvious

Wait with 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 small letter. Each consecive word in a variable’s
name starts with a capital letter

Avoid abbreviations

// Wrong

short Cntr;

char ITEM_DELIM = '\t';



// Correct

short counter;

char itemDelimiter = '\t';

Classes always start with a big letter. Public classes start with a ‘Q’ (QRgb). Public functions most often start with a ‘q’ (qRgb).

Whitespace

Use blank lines to group statements together where suited

Always use only one blank line

Always use a single space after a keyword, and before a curly brace.
```
// Wrong

if(foo){

}



// Correct

if (foo) {

}
```

For pointers or references, always use a single space before ‘*’ or ‘&’, but never after.

No space after a cast.

Avoid C-style casts when possible.

// Wrong

char* blockOfMemory = (char* ) malloc(data.size());



// Correct

char *blockOfMemory = (char *)malloc(data.size());

char *blockOfMemory = reinterpret_cast(malloc(data.size()));

Braces

As a base rule, the left curly brace goes on the same line as the start of the statement:
```
// Wrong

if (codec)

{

}



// Correct

if (codec) {

}
```

Exception: Function implementations and class declarations always have the left brace on the start of a line:
```
static void foo(int g)

{

    qDebug("foo: %i", g);

}



class Moo

{

};
```

Use curly braces when the body of a conditional statement contains more than one line,
and also if a single line statement is somewhat complex.

// Wrong

if (address.isEmpty()) {

    return false;

}



for (int i = 0; i &lt; 10; ++i) {

    qDebug("%i", i);

}



// Correct

if (address.isEmpty())

    return false;



for (int i = 0; i &lt; 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: 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) {}
```

Parentheses

Use parentheses to group expressions:

// Wrong

if (a && b || c)



// Correct

if ((a && b) || c)



// Wrong

a + b & c



// Correct

(a + b) & c

Switch statements

The case labels are on 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

switch (myEnum) {

case Value1:

    doSomething();

    break;

case Value2:

    doSomethingElse();

    // fall through

default:

    defaultHandling();

    break;

}

Line breaks

Keep lines shorter than 100 characters; insert
line breaks if necessary.

Commas go at the end of a broken line; operators start at the beginning of the new line. The operator is at the end of the line to avoid having to scroll if your editor is too narrow.

// Correct
if (longExpression
```
+ otherLongExpression

+ otherOtherLongExpression) {
```
}

// Wrong
if (longExpression +
```
otherLongExpression +

otherOtherLongExpression) {
```
}

General exception

Feel free to break a rule if it makes your code look bad.

官方 Qt 编码标准