1. Aspect Oriented
Programming
楊維中 a.k.a zonble
zonble@gmail.com
Thursday, September 12,

2. zonble
愛羅武勇
Thursday, September 12,

3. 羅馬不是一天造成的
Unmaintainable 的 code 也是
Thursday, September 12,

4. ⼀一開始，程式邏輯就只有插
⼊入資料⽽而已…
- (void)appendData:(NSData *)inData {
[_data appendData:inData];
}
Thursday, September 12,

5. 後來，我們想確定傳⼊入的不
是 nil 或空資料
- (void)appendData:(NSData *)inData {
NSParameterAssert(inData != nil);
NSParameterAssert([inData length]);
length = [_data length];
[_data appendData:inData];
NSAssert(length != [_data length]);
}
Thursday, September 12,

6. 後來，我們覺得 Release Build
也應該防⽌止輸⼊入空資料…
- (void)appendData:(NSData *)inData {
NSParameterAssert(inData != nil);
NSParameterAssert([inData length]);
if (!inData) { return; }
if (![inData length]) { return; }
length = [_data length];
[_data appendData:inData];
NSAssert(length != [_data length]);
}
Thursday, September 12,

7. 後來，我們發現這個 method
可能會在很多 thread 呼叫…
- (void)appendData:(NSData *)inData {
NSParameterAssert(inData != nil);
NSParameterAssert([inData length]);
if (!inData) {
NSLog(@"inData is nil!");
return;
}
if (![inData length]) {
NSLog(@"Length of inData is 0!");
return;
}
length = [_data length];
[_lock lock];
[_data appendData:inData];
[_lock unlock];
NSAssert(length != [_data length]);
}
Thursday, September 12,

8. 後來，在 Debug Build 裡頭要
加上 TestFlight CheckPoint
- (void)appendData:(NSData
*)inData {
NSParameterAssert(inData !=
nil);
NSParameterAssert([inData
length]);
if (!inData) {
NSLog(@"inData is nil!");
return;
}
if (![inData length]) {
NSLog(@"Length of inData
is 0!");
return;
}
length = [_data length];
[_lock lock];
[_data appendData:inData];
[_lock unlock];
NSAssert(length != [_data
length]);
#if DEBUG
[TestFlight
passCheckpoint:@"APPEND_DATA"];
#endif
}
Thursday, September 12,

9. Release Build 則要加上 Flurry
Event Log…
- (void)appendData:(NSData
*)inData {
NSParameterAssert(inData !=
nil);
NSParameterAssert([inData
length]);
if (!inData) {
NSLog(@"inData is nil!");
return;
}
if (![inData length]) {
NSLog(@"Length of inData
is 0!");
return;
}
length = [_data length];
[_lock lock];
[_data appendData:inData];
[_lock unlock];
NSAssert(length != [_data
length]);
#if DEBUG
[TestFlight
passCheckpoint:@"APPEND_DATA"];
#else
[Flurry
logEvent:@"APPEND_DATA"];
#endif
}
Thursday, September 12,

10. 還有 Google Analytics…
- (void)appendData:(NSData
*)inData {
NSParameterAssert(inData !=
nil);
NSParameterAssert([inData
length]);
if (!inData) {
NSLog(@"inData is nil!");
return;
}
if (![inData length]) {
NSLog(@"Length of inData
is 0!");
return;
}
length = [_data length];
[_lock lock];
[_data appendData:inData];
[_lock unlock];
NSAssert(length != [_data
length]);
#if DEBUG
[TestFlight
passCheckpoint:@"APPEND_DATA"];
#else
[Flurry
logEvent:@"APPEND_DATA"];
id<GAITracker>tracker = [[GAI
sharedInstance] defaultTracker];
[tracker send:
[[GAIDictionaryBuilder
createEventWithCategory:@"data"
withAction:@"append"
withLabel:@"user_data"
withValue:nil] build]];
#endif
}
Thursday, September 12,

11. 每件事情都很重要
• 確定傳⼊入參數的型態與內容
• 確定真的有插⼊入資料
• 加 Lock
• 加 Debug Log
• 加 TestFlight Log、Flurry Log…
Thursday, September 12,

12. 23 ⾏行 code 中，
做正事的只有一行。
這還不是最糟的…
Thursday, September 12,

13. 更糟的是…
不只⼀一個 method 這樣
Thursday, September 12,

14. 還會破壞程式的重用
Thursday, September 12,

15. 上個世紀末，就有⼈人覺得…
這樣不行
接下來的故事請⾃自⼰己查 Wikipedia
Thursday, September 12,

16. AOP 的基本想法：
把各種硬插進來的
Code 抽離並封裝
⽅方法很多
Thursday, September 12,

17. Cross-cutting concerns
…就是這些
• 確定傳⼊入參數的型態與內容
• 確定真的有插⼊入資料
• 加 Lock
• 加 Debug Log
• 加 TestFlight Log、Flurry Log…
Thursday, September 12,

18. Advice
在原本程式前後
插⼊入的程式碼
Thursday, September 12,

19. Decorator
Syntax
…Objective C 不⽀支援
Thursday, September 12,

20. Decorator Syntax
def add(x):
print "x:" + str(x)
result = x + 1
print "result:" + str(result)
return result
Thursday, September 12,

21. Decorator Syntax
def log(func):
def inner_func(*a):
print "args:" + str(a)
result = func(*a)
print "result:" + str(result)
return inner_func
@log
def add(x):
return x + 1
Thursday, September 12,

22. Objective-C 特性
Message
Forwarding
當⼀一個物件不⽀支援某個 Selector 的時
候，這個物件可以決定把 Selector 交給
其他的物件。
Thursday, September 12,

23. Message Forwarding
- (void)forwardInvocation:(NSInvocation *)anInvocation {
if ([someOtherObject respondsToSelector:
[anInvocation selector]])
// Advice here
[anInvocation invokeWithTarget:someOtherObject];
// Advice here
else
[super forwardInvocation:anInvocation];
}
See: Objective-C Runtime Programming Guide
Thursday, September 12,

24. AOP-in-Objective-C
https://github.com/moszi/AOP-in-
Objective-C
Thursday, September 12,

25. Method
Swizzling
Thursday, September 12,

26. Objective-C 第⼀一課
• ObjC 物件都是 C Structure
• ObjC method 都是 C function pointer
• 系統有⼀一個動態的索引表格，決定執⾏行
某個 selector 時，要對應到哪個 C
function
• Selector 就是索引表中的 key，型態為 C
字串
Thursday, September 12,

27. Objective-C 第⼆二課
• ⼀一個 Class 有哪些 method，都是在
runtime 的時候建⽴立的
• 所以可以在 runtime 新增新的 method，
例如使⽤用 category 語法
• 也可以直接使⽤用 runtime API 把已經存在
的 method 換掉
Thursday, September 12,

28. <objc/runtime.h>
BOOL class_addMethod(Class cls, SEL name,
IMP imp, const char *types);
IMP method_setImplementation(Method method,
IMP imp);
Thursday, September 12,

29. Thursday, September 12,

30. Thursday, September 12,

31. Thursday, September 12,

32. AOP-for-Objective-C
https://github.com/ndcube/AOP-for-
Objective-C/
在繼承關係的部份有些 bug，我⾃自⼰己有
先修，但是還沒有送 pull request…
Thursday, September 12,

33. Thank you!
Thursday, September 12,