ios 利用運行時 防崩潰 自動防止數組越界 字符串為空

運行時是一個好東西,他可以幫助我們解決很多的問題.在平時的開發中可能用的不是很多.但是做為APP開發人員遇到的崩潰情況肯定很多了.大致分為兩類 ?一類是由于代碼不嚴謹導致的數組越界 ? 一類是對字符串為空的情況下沒有判斷. ?這是本人遇到最多的崩潰情況了.解決好這個兩個,基本上APP就不會崩潰.那么那么多的對數組操作以及字符串操作一個一個做判斷嗎? ? ?當然這是我們應該做的,但是也有更好的以及方便的處理方式

提醒一下:

1、不要過分相信服務器返回的數據會永遠的正確。

2、在對數據處理上，要進行容錯處理，進行相應判斷之后再處理數據，這是一個良好的編程習慣。

3.老板讓你明天上線,你還沒有做容錯處理.所謂閻王叫你三更死......都是累,淚........

主要技術點:

運行時:導入框架

```

#import <objc/runtime.h>

```

這里主要通過runtime的method swizzling 交換方法的實現 提前判斷方法的參數是否符合要求 ? 在創建創建類當中的load方法里面利用單例交換數組字典等方法,替換成自己的方法,方便對參數做出相應的處理 .打個比方,檢測到參數為nil的時候直接return ? .就有效的防止了崩潰

```

+ (void)swizzleInstanceMethodWithClass:(Class)class

originalSelector:(SEL)originalSelector

swizzledMethod:(SEL)swizzledSelector {

Method originalMethod = class_getInstanceMethod(class, originalSelector);

Method swizzledMethod = class_getInstanceMethod(class, swizzledSelector);

if (class_addMethod(class, originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))) {

class_replaceMethod(class, swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));

}else {

method_exchangeImplementations(originalMethod, swizzledMethod);

}

}

+ (void)load {

static dispatch_once_t onceToken;

dispatch_once(&onceToken, ^{

//? ? ? ? NSArray

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayI") originalSelector:@selector(objectAtIndex:) swizzledMethod:@selector(fcx_safeObjectAtIndex:)];

//? ? ? ? NSMutableArray

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM") originalSelector:@selector(objectAtIndex:) swizzledMethod:@selector(fcx_safeObjectAtIndex:)];

//? ? ? ? [self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM") originalSelector:@selector(addObject:) swizzledMethod:@selector(fcx_safeAddObject:)];

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM") originalSelector:@selector(replaceObjectAtIndex:withObject:) swizzledMethod:@selector(fcx_safeReplaceObjectAtIndex:withObject:)];

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM") originalSelector:@selector(insertObject:atIndex:) swizzledMethod:@selector(fcx_safeInsertObject:atIndex:)];

//? ? ? ? NSDictionary

//? ? ? ? [self swizzleClassMethodWithClass:[NSDictionary class] originalSelector:@selector(dictionaryWithObjects:forKeys:count:) swizzledMethod:@selector(fcx_safeDictionaryWithObjects:forKeys:count:)];

//? ? ? ? NSMutableDictionary

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSDictionaryM") originalSelector:@selector(setObject:forKey:) swizzledMethod:@selector(fcx_safeSetObject:forKey:)];

});

}

```

這里對字典賦值進行一個講解,大家可以舉一反三去思考.后面會直接提供代碼.

在前面的單例中我們已經利用swizzling 將setObject:forKey: 這個方法替換成了我們自己的方法(fcx_safeSetObject:forKey:

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSDictionaryM") originalSelector:@selector(setObject:forKey:) swizzledMethod:@selector(fcx_safeSetObject:forKey:)];

//替換之后的方法 ? 通俗講就是我們利用對字段賦值的時候會直接調用下面的方法

```

- (void)fcx_safeSetObject:(id)anObject forKey:(id)aKey {

//如果字典的key值為空則 return ??

if (!aKey)

{

FCXSCLOG(@"[%@ %@] nil key. key cannot be nil", NSStringFromClass([self class]), NSStringFromSelector(_cmd));

return;

}

//如果字典的key值為空則 return

if (!anObject)

{

FCXSCLOG(@"[%@ %@] nil object. object cannot be nil", NSStringFromClass([self class]), NSStringFromSelector(_cmd));

return;

}

[self fcx_safeSetObject:anObject forKey:aKey];

}

```

當然各位也可以根據自己的需求進行相應的處理.下面是源碼.供大家參考 ??

//溫馨提示直接創建一個FCXSafeCollection類 ?然后將下面代碼全部粘貼到.m文件拖動工程即可

```

#import "FCXSafeCollection.h"

#import

#if DEBUG

#defineFCXSCLOG(...) fcxSafeCollectionLog(__VA_ARGS__)

#else

#defineFCXSCLOG(...)

#endif

voidfcxSafeCollectionLog(NSString *fmt, ...) NS_FORMAT_FUNCTION(1, 2);

voidfcxSafeCollectionLog(NSString *fmt, ...)

{

va_list ap;

va_start(ap, fmt);

NSString *content = [[NSString alloc] initWithFormat:fmtarguments:ap];

NSLog(@"***Terminating app due touncaught exception\n");

NSLog(@"***reason:-%@", content);

va_end(ap);

NSLog(@"*** First throw callstack:\n%@", [NSThread callStackSymbols]);

}

#pragmamark - NSArray

@interfaceNSArray (Safte)

@end

@implementationNSArray (Safte)

- (id)fcx_safeObjectAtIndex:(NSUInteger)index{

if (self.count > index) {

return [self fcx_safeObjectAtIndex:index];

}else {

FCXSCLOG(@"[%@ %@] index %lubeyond bounds [0 .. %lu]",

NSStringFromClass([selfclass]),

NSStringFromSelector(_cmd),

(unsigned long)index,

MAX((unsigned long)self.count- 1, 0));

return nil;

}

}

@end

//**************************************************************

#pragmamark - NSMutableArray

@interfaceNSMutableArray (Safte)

@end

@implementationNSMutableArray (Safte)

- (id)fcx_safeObjectAtIndex:(NSUInteger)index{

if (self.count > index) {

return [self fcx_safeObjectAtIndex:index];

}else {

FCXSCLOG(@"[%@ %@] index %lubeyond bounds [0 .. %lu]",

NSStringFromClass([selfclass]),

NSStringFromSelector(_cmd),

(unsigned long)index,

MAX((unsigned long)self.count - 1, 0));

return nil;

}

}

- (void)fcx_safeAddObject:(id)anObject{

if (anObject) {

[self fcx_safeAddObject:anObject];

}else {

FCXSCLOG(@"[%@ %@], nil object.object cannot be nil", NSStringFromClass([self class]),NSStringFromSelector(_cmd));

}

}

- (void)fcx_safeReplaceObjectAtIndex:(NSUInteger)indexwithObject:(id)anObject {

if (index >= self.count) {

FCXSCLOG(@"[%@ %@] index %lubeyond bounds [0 .. %lu].",

NSStringFromClass([selfclass]),

NSStringFromSelector(_cmd),

(unsigned long)index,

MAX((unsigned long)self.count- 1, 0));

return;

}else if (!anObject) {

FCXSCLOG(@"[%@ %@] nil object.object cannot be nil", NSStringFromClass([self class]),NSStringFromSelector(_cmd));

return;

}

[self fcx_safeReplaceObjectAtIndex:index withObject:anObject];

}

- (void)fcx_safeInsertObject:(id)anObjectatIndex:(NSUInteger)index {

if (index > self.count)

{

FCXSCLOG(@"[%@ %@] index %lubeyond bounds [0...%lu].",

NSStringFromClass([selfclass]),

NSStringFromSelector(_cmd),

(unsigned long)index,

MAX((unsigned long)self.count- 1, 0));

return;

}

if (!anObject)

{

FCXSCLOG(@"[%@ %@] nil object.object cannot be nil", NSStringFromClass([self class]),NSStringFromSelector(_cmd));

return;

}

[self fcx_safeInsertObject:anObject atIndex:index];

}

@end

//**************************************************************

#pragmamark - NSDictionary

@interfaceNSDictionary (Safte)

@end

@implementationNSDictionary (Safte)

+ (instancetype)fcx_safeDictionaryWithObjects:(constid_Nonnull __unsafe_unretained*)objects forKeys:(const id_Nonnull __unsafe_unretained *)keys count:(NSUInteger)cnt {

id validObjects[cnt];

id validKeys[cnt];

NSUInteger count = 0;

for (NSUInteger i = 0; i < cnt; i++)

{

if (objects[i] && keys[i])

{

validObjects[count] = objects[i];

validKeys[count] = keys[i];

count ++;

}

else

{

FCXSCLOG(@"[%@ %@] NIL objector key at index{%lu}.",

NSStringFromClass(self),

NSStringFromSelector(_cmd),

(unsigned long)i);

}

}

return [self fcx_safeDictionaryWithObjects:validObjectsforKeys:validKeys count:count];

}

@end

//**************************************************************

#pragmamark - NSMuatbleDictionary

@interfaceNSMutableDictionary (Safte)

@end

@implementationNSMutableDictionary (Safte)

- (void)fcx_safeSetObject:(id)anObjectforKey:(id)aKey {

if (!aKey)

{

FCXSCLOG(@"[%@ %@] nil key. keycannot be nil", NSStringFromClass([self class]), NSStringFromSelector(_cmd));

return;

}

if (!anObject)

{

FCXSCLOG(@"[%@ %@] nil object.object cannot be nil", NSStringFromClass([self class]), NSStringFromSelector(_cmd));

return;

}

[self fcx_safeSetObject:anObject forKey:aKey];

}

@end

//**************************************************************

@implementationFCXSafeCollection

+ (void)load{

static dispatch_once_t onceToken;

dispatch_once(&onceToken, ^{

//NSArray

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayI")originalSelector:@selector(objectAtIndex:) swizzledMethod:@selector(fcx_safeObjectAtIndex:)];

//NSMutableArray

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM")originalSelector:@selector(objectAtIndex:) swizzledMethod:@selector(fcx_safeObjectAtIndex:)];

//[selfswizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM")originalSelector:@selector(addObject:)swizzledMethod:@selector(fcx_safeAddObject:)];

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM")originalSelector:@selector(replaceObjectAtIndex:withObject:) swizzledMethod:@selector(fcx_safeReplaceObjectAtIndex:withObject:)];

[self swizzleInstanceMethodWithClass:NSClassFromString(@"__NSArrayM")originalSelector:@selector(insertObject:atIndex:) swizzledMethod:@selector(fcx_safeInsertObject:atIndex:)];

//NSDictionary

//[selfswizzleClassMethodWithClass:[NSDictionary class]originalSelector:@selector(dictionaryWithObjects:forKeys:count:)swizzledMethod:@selector(fcx_safeDictionaryWithObjects:forKeys:count:)];

//NSMutableDictionary

[selfswizzleInstanceMethodWithClass:NSClassFromString(@"__NSDictionaryM") originalSelector:@selector(setObject:forKey:)swizzledMethod:@selector(fcx_safeSetObject:forKey:)];

});

}

+ (void)swizzleInstanceMethodWithClass:(Class)class

originalSelector:(SEL)originalSelector

swizzledMethod:(SEL)swizzledSelector{

Method originalMethod = class_getInstanceMethod(class,originalSelector);

Method swizzledMethod = class_getInstanceMethod(class,swizzledSelector);

if (class_addMethod(class,originalSelector, method_getImplementation(swizzledMethod), method_getTypeEncoding(swizzledMethod))){

class_replaceMethod(class,swizzledSelector, method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));

}else {

method_exchangeImplementations(originalMethod,swizzledMethod);

}

}

+ (void)swizzleClassMethodWithClass:(Class)class

originalSelector:(SEL)originalSelector

swizzledMethod:(SEL)swizzledSelector{

Method originalMethod = class_getClassMethod(class,originalSelector);

Method swizzledMethod = class_getClassMethod(class,swizzledSelector);

//if (class_addMethod(class, originalSelector,method_getImplementation(swizzledMethod),method_getTypeEncoding(swizzledMethod))) {

//

//class_replaceMethod(class, swizzledSelector,method_getImplementation(originalMethod), method_getTypeEncoding(originalMethod));

//}else {

//

method_exchangeImplementations(originalMethod,swizzledMethod);

//}

}

@end

#pragmamark - KeyValueSafeCollections

@interfaceNSObject (FCXKeyValueSafeCollections)

@end

@implementationNSObject (FCXKeyValueSafeCollections)

//當對一個非類對象屬性設置nil時，就會執行setNilValueForKey:方法,setNilValueForKey:方法的默認實現,是產生一個NSInvalidArgumentException的異常,但是你可以重寫這個方法.

- (void)setNilValueForKey:(NSString*)key {

FCXSCLOG(@"[%@ %@]: could not set nilas the value for the key %@.", NSStringFromClass([self class]),NSStringFromSelector(_cmd), key);

}

```

//如果沒有對應的訪問器方法(setter方法),如果接受者的類的+accessInstanceVariablesDirectly方法返回YES,那么就查找這個接受者的與key相匹配的實例變量(匹配模式為_,_is,,is):比如:key為age,只要屬性存在_age,_isAge,age,isAge中的其中一個就認為匹配上了,如果找到這樣的一個實例變量,并且的類型是一個對象指針類型,首先released對象上的舊值,然后把傳入的新值retain后的傳入的值賦值該成員變量,如果方法的參數類型是NSNumber或NSValue的對應的基本類型,先把它轉換為基本數據類,再執行方法,傳入轉換后的數據.

//+(BOOL)accessInstanceVariablesDirectly {

//return YES;

//}

//對于數據模型中缺少的、不能與任何鍵配對的屬性的時候，系統會自動調用setValue:forUndefinedKey:這個方法，該方法默認的實現會引發一個NSUndefinedKeyExceptiony異常,但是我們可以重寫setValue:forUndefinedKey:方法讓程序在運行過程中不引發任何異常信息且正常工作

- (void)setValue:(id)valueforUndefinedKey:(NSString *)key {

FCXSCLOG(@"[%@ %@]: this class is notkey value coding-compliant for the key %@.", NSStringFromClass([selfclass]), NSStringFromSelector(_cmd), key);

}

//通過valueForKey獲取對象屬性值的方法時，如果代碼中的key值不存在，系統會自動調用valueForUndefinedKey:這個方法，該方法默認的實現會引發一個NSUndefinedKeyExceptiony異常,但是我們可以重寫valueForUndefinedKey:方法讓程序在運行過程中不引發任何異常信息且正常工作

/**

*通過valueForKey獲取對象屬性值的方法時，如果代碼中的key值不存在，系統會自動調用valueForUndefinedKey:這個方法，該方法默認的實現會引發一個NSUndefinedKeyExceptiony異常,但是我們可以重寫valueForUndefinedKey:方法讓程序在運行過程中不引發任何異常信息且正常工作

*

*@return nil

*

*@notice雖然這步可以返回nil不閃退，但是后續操作依然可能有問題

*/

- (id)valueForUndefinedKey:(NSString*)key {

FCXSCLOG(@"[%@ %@]: this class is notkey value coding-compliant for the key %@.", NSStringFromClass([selfclass]), NSStringFromSelector(_cmd), key);

return nil;

}

@end


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