在iOS开发过程中, 我们可能会碰到一些系统方法弃用, weak、循环引用、不能执行之类的警告，运用clang标注可以帮助你轻松解决。
// 插入需要忽略的相关代码 ⚠️
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Wundeclared-selector"
//插入需要忽略的相关代码（test方法在本类中不存在，ignored后加入"-Wundeclared-selector"编译器便忽略了此警告。）
[one performSelector:@selector(test) withObject:nil afterDelay:2.0];
#pragma clang diagnostic pop
//方法弃用告警 ⚠️
#pragmaclang diagnostic push
#pragmaclang diagnostic ignored "-Wdeprecated-declarations"
UIAlertView *alertViewTmp = [[UIAlertView alloc]initWithTitle:@""message:@""delegate:nil cancelButtonTitle:@""otherButtonTitles:@"", nil];
[alertViewTmp show];
#pragmaclang diagnostic pop
// 不兼容指针类型 ⚠️
#pragmaclang diagnostic push
#pragmaclang diagnostic ignored "-Wincompatible-pointer-types"
//
#pragmaclang diagnostic pop
//循环引用 ⚠️
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-retain-cycles"
// self.completionBlock = ^ {//...// };
#pragma clang diagnostic pop
// 未使用变量 ⚠️
#pragmaclang diagnostic push
#pragmaclang diagnostic ignored "-Wunused-variable"
// inta;
#pragmaclang diagnostic pop
// 未使用default ⚠️
#pragmaclang diagnostic push
#pragmaclang diagnostic ignored "-Wcovered-switch-default"
// switch (style) {
// case UITableViewCellStyleDefault:
// case UITableViewCellStyleValue1:
// case UITableViewCellStyleValue2:
// case UITableViewCellStyleSubtitle:
// // ...
// default:
// return;
// }
#pragmaclang diagnostic pop
大家可以搜索需要忽略的警告编号，替换-Wundeclared-selector。（以下部分仅供参考）
-Wformat invalid position specified for %select{field width|field precision}0
-Wformat cannot mix positional and non-positional arguments in format string
-Wformat values of type '%0' should not be used as format arguments add an explicit cast to %1 instead
-Wformat format specifies type %0 but the argument has type %1
-Wformat zero field width in scanf format string is unused
-Wformat no closing ']' for '%%[' in scanf format string
-Wformat format string should not be a wide string
-Wformat format string contains '\\0' within the string body
-Wformat '%select{*|.*}0' specified field %select{width|precision}0 is missing a matching 'int' argument
-Wformat field %select{width|precision}0 should have type %1, but argument has type %2
-Wformat %select{field width|precision}0 used with '%1' conversion specifier, resulting in undefined behavior
-Wformat format string missing
-Wformat incomplete format specifier-Wformat flag '%0' results in undefined behavior with '%1' conversion specifier
-Wformat flag '%0' is ignored when flag '%1' is present-Wformat more '%%' conversions than data arguments
-Wformat length modifier '%0' results in undefined behavior or no effect with '%1' conversion specifier
-Wformat-extra-args data argument not used by format string
-Wformat-invalid-specifier invalid conversion specifier '%0'
-Wformat-nonliteral format string is not a string literal
-Wformat-security format string is not a string literal (potentially insecure)
-Wformat-zero-length format string is empty
-Wgcc-compat GCC does not allow the 'cleanup' attribute argument to be anything other than a simple identifier
-Wglobal-constructors declaration requires a global constructor
-Wglobal-constructors declaration requires a global destructor
-Wgnu-conditional-omitted-operand use of GNU ?: conditional expression extension, omitting middle operand
-Wheader-hygiene using namespace directive in global context in header
-Widiomatic-parentheses using the result of an assignment as a condition without parentheses
-Wignored-attributes 'malloc' attribute only applies to functions returning a pointer type
-Wignored-attributes %0 attribute only applies to %select{functions|unions|variables and functions|functions and methods|parameters|functions, methods and blocks|functions, methods, and classes|functions, methods, and parameters|classes|variables|methods|variables, functions and labels|fields and global variables|structs|variables, functions and tag types|thread-local variables|variables and fields|variables, data members and tag types|types and namespaces|Objective-C interfaces}1
-Wignored-attributes '%0' attribute cannot be specified on a definition
-Wignored-attributes __weak attribute cannot be specified on an automatic variable when ARC is not enabled
-Wignored-attributes Objective-C GC does not allow weak variables on the stack
-Wignored-attributes __weak attribute cannot be specified on a field declaration
-Wignored-attributes attribute %0 cannot be applied to %select{functions|Objective-C method}1 without return value
-Wignored-attributes attribute declaration must precede definition
-Wignored-attributes attribute %0 is ignored, place it after \"%select{class|struct|union|interface|enum}1\" to apply attribute to type declaration
-Wignored-attributes __declspec attribute %0 is not supported
-Wignored-attributes attribute %0 ignored, because it cannot be applied to a type
-Wignored-attributes attribute %0 after definition is ignored
-Wignored-attributes %0 attribute ignored
-Wignored-attributes 'sentinel' attribute only supported for variadic %select{functions|blocks}0
-Wignored-attributes 'sentinel' attribute requires named arguments
-Wignored-attributes '%0' only applies to %select{function|pointer|Objective-C object or block pointer}1 types type here is %2
-Wignored-attributes 'nonnull' attribute applied to function with no pointer arguments
-Wignored-attributes %0 attribute can only be applied to instance variables or properties
-Wignored-attributes ibaction attribute can only be applied to Objective-C instance methods
-Wignored-attributes %0 calling convention ignored on variadic function
-Wignored-attributes %0 only applies to variables with static storage duration and functions
-Wignored-attributes %0 attribute argument not supported: %1
-Wignored-attributes #pramga ms_struct can not be used with dynamic classes or structures
-Wignored-attributes transparent union definition must contain at least one field transparent_union attribute ignored
-Wignored-attributes first field of a transparent union cannot have %select{floating point|vector}0 type %1 transparent_union attribute ignored
-Wignored-attributes 'gnu_inline' attribute requires function to be marked 'inline', attribute ignored
