1.全局tableView分割线左右对齐
//设置全局cell分割线与屏幕等宽
[[UITableView appearance] setSeparatorStyle:UITableViewCellSeparatorStyleSingleLine];
[[UITableView appearance] setSeparatorInset:UIEdgeInsetsZero];
[[UITableViewCell appearance] setSeparatorInset:UIEdgeInsetsZero];

if ([UITableView instancesRespondToSelector:@selector(setLayoutMargins:)]) {
    [[UITableView appearance] setLayoutMargins:UIEdgeInsetsZero];
    [[UITableViewCell appearance] setLayoutMargins:UIEdgeInsetsZero];
    [[UITableViewCell appearance] setPreservesSuperviewLayoutMargins:NO];
}

2.强引用或者弱引用
/**
Synthsize a weak or strong reference.

Example:
@weakify(self)
[self doSomething^{
@strongify(self)
if (!self) return;
...
}];

*/

ifndef weakify

#if DEBUG
    #if __has_feature(objc_arc)
    #define weakify(object) autoreleasepool{} __weak __typeof__(object) weak##_##object = object;
    #else
    #define weakify(object) autoreleasepool{} __block __typeof__(object) block##_##object = object;
    #endif
#else
    #if __has_feature(objc_arc)
    #define weakify(object) try{} @finally{} {} __weak __typeof__(object) weak##_##object = object;
    #else
    #define weakify(object) try{} @finally{} {} __block __typeof__(object) block##_##object = object;
    #endif
#endif

endif

ifndef strongify

#if DEBUG
    #if __has_feature(objc_arc)
    #define strongify(object) autoreleasepool{} __typeof__(object) object = weak##_##object;
    #else
    #define strongify(object) autoreleasepool{} __typeof__(object) object = block##_##object;
    #endif
#else
    #if __has_feature(objc_arc)
    #define strongify(object) try{} @finally{} __typeof__(object) object = weak##_##object;
    #else
    #define strongify(object) try{} @finally{} __typeof__(object) object = block##_##object;
    #endif
#endif

endif

3.处理编译器警告

pragma clang diagnostic push

pragma clang diagnostic ignored "-相关命令"

// 你自己的代码

pragma clang diagnostic pop

常用命令: "-Wdeprecated-declarations" ->方法弃用告警
"-Wincompatible-pointer-types" ->不兼容指针类型
"-Wunused-variable" ->未使用变量

4.方法弃用
DEPRECATED_ATTRIBUTE
DEPRECATED_MSG_ATTRIBUTE(msg)