译自：http://nshipster.com/new-years-2015/
成员函数的秘密
swift类和结构体的成员函数总是有以下2种等价调用形式：
[1, 2, 3, 4].reverse()
Array.reverse([1, 2, 3, 4])()
@()封装C字符串
除了封装数字和用在集合上，还可用于char *
NSString *propertyAttributesString =
@(property_getAttributes(class_getProperty([NSObject class], "description")));
//输出：T@"NSString",R,C
AmIBeingDebugged
判断app是否在调试器下运行的函数
#include <assert.h>
#include <stdbool.h>
#include <sys/types.h>
#include <unistd.h>
#include <sys/sysctl.h>
static bool AmIBeingDebugged(void) {
int mib[4];
struct kinfo_proc info;
size_t size = sizeof(info);
info.kp_proc.p_flag = 0;
mib[0] = CTL_KERN;
mib[1] = KERN_PROC;
mib[2] = KERN_PROC_PID;
mib[3] = getpid();
sysctl(mib, sizeof(mib) / sizeof(*mib), &info, &size, NULL, 0);
return (info.kp_proc.p_flag & P_TRACED) != 0;
}
使用延迟变量
尽量避免声明optional变量，但没有初始值怎么办，使用lazy关键字，谨记在有实际值前不要调用getter，例如：
lazy var someModelStructure = ExpensiveClass()
如果在调用getter前调用了setter，则ExpensiveClass()永远不会执行。适用于viewDidLoad里才初始化的IBOutlet视图
获取插入到storyboard的容器视图的子控制器
// 1. A property has the same name as a segue identifier in XIB
@property (nonatomic) ChildViewController1 *childController1;
@property (nonatomic) ChildViewController2 *childController2;
// #pragma mark - UIViewController
- (void)prepareForSegue:(UIStoryboardSegue *)segue
sender:(id)sender
{
[super prepareForSegue:segue sender:sender];
// 2. All known destination controllers assigned to properties
if ([self respondsToSelector:NSSelectorFromString(segue.identifier)] ) {
[self setValue:segue.destinationViewController forKey:segue.identifier];
}
}
- (void)viewDidLoad
{
[super viewDidLoad];
// 3. Controllers already available bc viewDidLoad is called after prepareForSegue
self.childController1.view.backgroundColor = [UIColor redColor];
self.childController2.view.backgroundColor = [UIColor blueColor];
}
不编译重运行
Product > Perform Action > Run without Building
快捷键：⌘⌃R
快速获取Playground资源文件
Playground共享同一数据文件夹：/HOME/Documents/Shared Playground Data，以下为获取资源文件路径的方法：
import XCPlayground
func pathToFileInSharedSubfolder(file: String) -> String {
return XCPSharedDataDirectoryPath + "/" + NSProcessInfo.processInfo().processName + "/" + file
}
processName即为Playground文件名，例如要获取本地json数据：
var jsonReadError:NSError?
let jsonData = NSFileManager.defaultManager().contentsAtPath(pathToFileInSharedSubfolder("data.json"))!
let jsonArray = NSJSONSerialization.JSONObjectWithData(jsonData, options: nil, error: &jsonReadError) as [AnyObject]
CocoaPods
查看app所使用的所有pods：
class-dump -C Pods_ /Applications/Squire.app | grep -o "Pods_\w+"
阻止dylib Hooking
在项目设置Other Linker Flags里添加：
-Wl,-sectcreate,__RESTRICT,__restrict,/dev/null
获取app运行使用的语言
[[NSBundle mainBundle] preferredLocalizations]
NSDateFormatter +dateFormatFromTemplate:options:locale:
日期格式化模板例子：
NSLocale *usLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_US"];
NSLocale *gbLocale = [[NSLocale alloc] initWithLocaleIdentifier:@"en_GB"];
NSString *dateFormat;
NSString *dateComponents = @"yMMMMd";
dateFormat = [NSDateFormatter dateFormatFromTemplate:dateComponents options:0 locale:usLocale];
NSLog(@"Date format for %@: %@",
[usLocale displayNameForKey:NSLocaleIdentifier value:[usLocale localeIdentifier]], dateFormat);
dateFormat = [NSDateFormatter dateFormatFromTemplate:dateComponents options:0 locale:gbLocale];
NSLog(@"Date format for %@: %@",
[gbLocale displayNameForKey:NSLocaleIdentifier value: [gbLocale localeIdentifier]], dateFormat);
// Output:
// Date format for English (United States): MMMM d, y
// Date format for English (United Kingdom): d MMMM y
通过lldb获得内部常量
获得转场动画的持续时间：
- 设置断点：
(lldb) br set -n "+[UITransitionView defaultDurationForTransition:]" - 展示模态视图以触发断点，然后执行：
(lldb) finish - 从xmm0寄存器读取结果：
(lldb) register read xmm0 --format float64，输出xmm0 = {0.4 0}，0.4即为持续时间
自定义弱引用关联对象
@interface WeakObjectContainter : NSObject
@property (nonatomic, readonly, weak) id object;
@end
@implementation WeakObjectContainter
- (instancetype)initWithObject:(id)object {
self = [super init];
if (!self) {
return nil;
}
self.object = object;
return self;
}
@end
使用：
objc_setAssociatedObject(self, &MyKey, [[WeakObjectContainter alloc] initWithObject:object], OBJC_ASSOCIATION_RETAIN_NONATOMIC)
获取弱引用对象：
id object = [objc_getAssociatedObject(self, &MyKey) object];