1.do{...}while(0)妙用.
當(dāng)我們的方法想返回一個(gè)對(duì)象,但首先不知道對(duì)象是否已經(jīng)創(chuàng)建好,或者說(shuō)有很多異常處理機(jī)制去返回,有一部分代碼只需要執(zhí)行一部分隨時(shí)想要返回,但是又不好使用goto,因?yàn)殡y以理解,這個(gè)時(shí)候可以用do{...}while(0).
- (id)findServiceByName:(NSString *)name
{
id <DTService> service = nil;
do {
if (name == nil || [name length] == 0) {
[NSException raise:NSInvalidArgumentException format:@"The parameter: \"name\" MUST NOT be empty."];
break;
}
// 如果找到該服務(wù)书蚪,并且不是一個(gè)延遲加載的服務(wù)擦俐,則返回該服務(wù)對(duì)象烤惊。
DFServiceInfo *info = [self.serviceMap objectForKey:name];
if (info == nil) {
NSLog(@"The service specified by name '%@' not found.", name);
break;
}
// 優(yōu)化:減少加鎖造成效率的問(wèn)題
if (info.object) {
service = info.object;
break;
}
@synchronized(info) {
service = info.object;
if (service) {
break;
}
if (info.cls) {
APLogMonitor(@"##BOOT##", @"serviceLoad begin %@ - %@", name, [NSThread currentThread]);
// APLogInfo(@"##BOOTMONITOR##",@"serviceLoad begin %@ - %@", name, [NSThread currentThread]);
service = [[info.cls alloc] init];
if (service && [(id)service respondsToSelector:@selector(start)]) {
NSLog(@"start service %@",name);
[service start];
}
else {
NSLog(@"Cannot create service specified by name: %@", NSStringFromClass(info.cls));
}
info.object = service;
// APLogInfo(@"##BOOTMONITOR##", @"serviceLoad end %@", name);
APLogMonitor(@"##BOOT##", @"serviceLoad end %@", name);
}
}
} while (0);
return service;
}
2.方法批處理
需要批量處理方法的時(shí)候,我們簡(jiǎn)單的采取方法調(diào)用的方式進(jìn)行,這里提供一個(gè)更加科學(xué)和簡(jiǎn)潔的代碼組織方式.
// 當(dāng)我們想要調(diào)用多個(gè)步驟的方法時(shí),采用如下方式
[self executePhases:@[[DTBootPhase setupWindow],
[DTBootPhase setupNavigationController],
[DTBootPhase startRunonceServices],
[DTBootPhase frameworkInit],
[DTBootPhase showWindow],
[DTBootPhase startLauncher]]];
// DTBootPhase這個(gè)類把一個(gè)方法抽象成一個(gè)name和一個(gè)block類型(DTBootPhase)保存起來(lái).但代碼并未開(kāi)始執(zhí)行.
+ (DTBootPhase*)phaseWithName:(NSString*)name block:(DTBootPhaseBlock)block
{
DTBootPhase* phase = [[DTBootPhase alloc] init];
phase.name = name;
phase.block = block;
return phase;
}
// 把想要執(zhí)行的代碼創(chuàng)建成DTBootPhase類型.
+ (DTBootPhase*)setupWindow
{
return [DTBootPhase phaseWithName:@"setupWindow" block:^{
DTBootLoader* bootLoader = [[DTFrameworkInterface sharedInstance] bootLoader];
if (bootLoader.windowSetupDone)
return;
[DFContext sharedContext].window = [bootLoader createWindow];
bootLoader.windowSetupDone = YES;
}];
}
// 最后在執(zhí)行的時(shí)候,把數(shù)組里面的操作一次遍歷,方便打log和各種批處理.
- (void)executePhases:(NSArray<DTBootPhase*> *)phases
{
APLogInfo(@"##BOOTMONITOR##", @"executePhases");
for (DTBootPhase* phase in phases)
{
[phase execute];
APLogInfo(@"##BOOTMONITOR##", @"executePhase:%@", phase.name);
}
}
3.巧用({})讓代碼更加簡(jiǎn)潔
在返回一個(gè)對(duì)象的時(shí)候可以用({...})把一個(gè)代碼段包括起來(lái),代碼段最后返回一個(gè)對(duì)象,這個(gè)對(duì)象就是方法里面需要用的對(duì)象,這樣寫(xiě)避免了先定義后使用的時(shí)候代碼的繁雜,更加清晰可讀.
[self registerModel:({
_guessModel =[[O2OGuessYouLikeModel alloc] initWithViewController:self];
_guessModel.cityId = [[O2OLocationManager defaultManager] selectedCityInfoInternal].code;
_guessModel.labelId = self.initialLabelId;
_guessModel;
})];
4.使用NSPredicate進(jìn)行數(shù)據(jù)過(guò)濾
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"(blockId.length > 0)"];
NSArray *filteredBlocks = [result.blocks filteredArrayUsingPredicate:predicate];
5.防止數(shù)組越界方法,確認(rèn)數(shù)組可用方法寥院,更加安全的數(shù)組。
防止數(shù)組越界
/**
* DTExtensions for reading value at index
*/
@interface NSArray (DTExtensions)
- (id)objectOrNilAtIndex:(NSUInteger)index;
- (BOOL)containsIndex:(NSUInteger)index;
@end
/**
* DTExtensions for writing value at index
*/
@interface NSMutableArray (DTExtensions)
- (void)addObjectOrNil:(id)anObject;
- (BOOL)insertObjectOrNil:(id)anObject atIndex:(NSUInteger)index;
- (BOOL)replaceObjectAtIndex:(NSUInteger)index withObjectOrNil:(id)anObject;
@end
確認(rèn)數(shù)組可用
#define __IsStringValid(_str) (_str && [_str isKindOfClass:[NSString class]] && ([_str length] > 0))
#define __IsArrayValid(_array) (_array && [_array isKindOfClass:[NSArray class]] && ([_array count] > 0))
更安全的string
static inline NSString* __o2oString(id value, NSString* defaultString)
{
if ([value isKindOfClass:[NSString class]]) {
return value;
}
else if ([value isKindOfClass:[NSNumber class]]) {
NSNumber *num = (NSNumber *)value;
return [num stringValue];
}
if (!defaultString && ![defaultString isKindOfClass:[NSString class]])
{
defaultString = @"";
}
return defaultString;
}
static inline NSString* __o2oStringDefault(id value)
{
return __o2oString(value, nil);
}