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);
}