OCLint的部分規則（Basic 部分）
對OCLint的部分規則進行簡單翻譯解釋，有部分進行了驗證以及進一步分析、測試。OCLint其他相關內容如下：
1、bitwise operator in conditional
since:0.6 定義類傳送門～點擊
Checks for bitwise operations in conditionals. Although being written on purpose in some rare cases, bitwise opera- tions are considered to be too “smart”. Smart code is not easy to understand.
簡單解釋：OCLint認爲
位運算符可讀性不好
void example(int a, int b) {
if (a | b) {
}
if (a & b) {
}
}2、broken null check
since:0.7 定義類傳送門～點擊
The broken null check itself will crash the program.
簡單解釋：錯誤的null檢查會導致程序
crash。
void m(A *a, B *b) {
if (a != NULL || a->bar(b))
{
}
if (a == NULL && a->bar(b))
{
}
} PS：OC(objective-c)向空對象可以發消息，不會發生
crash，但是上面這樣的代碼的邏輯是錯誤的。
3、broken nil check
since:0.7 定義類傳送門～點擊
The broken nil check in Objective-C in some cases returns just the opposite result.
簡單解釋：Objective-C中判空，有些情況下會返回預期相反的結果
+ (void)compare:(A *)obj1 withOther:(A *)obj2 {
if (obj1 || [obj1 isEqualTo:obj2])
{
}
if (!obj1 && ![obj1 isEqualTo:obj2])
{
}
}PS：這樣寫應該是邏輯錯誤
4、broken oddness check
since:0.6 定義類傳送門～點擊
Checking oddness by x % 2 == 1won’t work for negative numbers. Use x & 1 == 1,or x % 2 != 0 instead.
簡單解釋：對數字奇數性進行檢查（x % 2 == 1），如果是負數，會有異常，應使用
x & 1 == 1或者x % 2 != 0
void example() {
if (x % 2 == 1) // violation
{
}
if (foo() % 2 == 1) // violation
{
}
}PS：在Objective-C 上的測試結果上看，並沒有什麼大的異常。應該主要的問題是負數進行取模區的結果不會出現正值。
比如（x % 2）的結果是-1或者0，
5、collapsible if statements
Since: 0.6 定義類傳送門～點擊
This rule detects instances where the conditions of two consecutive if statements can be combined into one in order to increase code cleanness and readability.
簡單解釋：兩個連續
if條件可以合併的應該合併，可以提高可讀性和代碼整潔。
void example(bool x, bool y){
if (x) // these two if statements can be
{
if (y) // combined to if (x && y)
{
foo();
}
}
}6、constant conditional operator
Since: 0.6 定義類傳送門～點擊
conditional operator whose conditionals are always true or always false are confusing.
簡單解釋：檢查始終爲
true或者false的操作，會使人疑惑。
void example() {
int a = 1 == 1 ? 1 : 0; // 1 == 1 is actually always true
}7、constant if expression
Since: 0.2 定義類傳送門～點擊
if statements whose conditionals are always true or always false are confusing.
簡單解釋：
if始終爲true或者false的操作，會使人疑惑。
void example(){
if (true) { // always true
foo();
}
if (1 == 0) { // always false
bar();
}
}8、 dead code
Since: 0.4 定義類傳送門～點擊
Code after return, break, continue, and throw statements is unreachable and will never be executed.
簡單解釋：在
return、break、continueandthrow之後的代碼都是無效的
void example(id collection) {
for (id it in collection) {
continue;
int i1; // dead code
}
return;
int i2; // dead code
}9、double negative
Since:0.6 定義類傳送門～點擊
There is no point in using a double negative, it is always positive.
簡單解釋：代碼中雙重否定沒有意義
void example() {
int b1 = !!1;
int b2 = ~~1;
}10、for loop should be while loop
Since:0.6 定義類傳送門～點擊
Under certain circumstances, some for loops can be simplified to while loops to make code more concise.
簡單解釋：在有些情況下使用
while比使用for更簡潔
void example(int a) {
for (; a < 100;) {
foo(a);
}
}11、 goto statement
Since:0.6 定義類傳送門～點擊
Go To Statement Considered Harmful
簡單解釋：
go to被認爲有害的
void example() {
A:
a();
goto A; // Considered Harmful
}12、jumbled incrementer
Since:0.7 定義類傳送門～點擊
Jumbled incrementers are usually typos. If it’s done on purpose, it’s very confusing for code readers.
簡單解釋：混亂的迭代器通常會出現錯誤，可讀性不好。
void aMethod(int a) {
for (int i = 0; i < a; i++) {
for (int j = 0; j < a; i++) { // references both 'i' and 'j'
}
}
}13、misplaced null check
Since:0.7 定義類傳送門～點擊
The null check is misplaced. In C and C++, sending a message to a null pointer could crash the program. When null is misplaced, either the check is useless or it’s incorrect.
簡單解釋：
C和C++在條件判斷的時候注意null判斷放在前面，邏輯短路。
void m(A *a, B *b) {
if (a->bar(b) && a != NULL) { // violation
}
if (a->bar(b) || !a) { // violation
}
}14、misplaced nil check
Since:0.7 定義類傳送門～點擊
The nil check is misplaced. In Objective-C, sending a message to a nil pointer simply does nothing. But code readers may be confused about the misplaced nil check.
簡單解釋：
Objective-C在條件判斷的時候注意nil判斷放在前面，邏輯短路。
+ (void)compare:(A *)obj1 withOther:(A *)obj2 {
if ([obj1 isEqualTo:obj2] && obj1) {
}
if (![obj1 isEqualTo:obj2] || obj1 == nil) {
}
}15、 multiple unary operator
Since:0.6 定義類傳送門～點擊
Multiple unary operator can always be confusing and should be simplified.
簡單解釋：多重的運算符不易理解，應該簡化。
void example() {
int b = -(+(!(~1)));
}16、return from finally block
Since:0.6 定義類傳送門～點擊
Returning from a finally block is not recommended.
簡單解釋：不建議在finally中返回
void example() {
@try {
foo();
}
@catch(id ex) {
bar();
}
@finally {
return; // this can discard exceptions.
}
}17、throw exception from finally block
Since:0.6 定義類傳送門～點擊
Throwing exceptions within a finally block may mask other exceptions or code defects.
簡單解釋：從finally塊拋出異常，可能忽略其他的錯誤
void example() {
@try {;}
@catch(id ex) {;}
@finally {
id ex1;
@throw ex1; // this throws an exception
NSException *ex2 = [NSException new];
[ex2 raise]; // this throws an exception, too
}
}