tips笔记总结

tableViewCell里面图片圆角离屏渲染解决方案

撰写一个UIImageView的分类,分类仿写SDWebImage里面加载图片的方法把图片加载下来后,通过另外一个UIImage分类用贝塞尔曲线切圆角处理,然后根据和SDWebImage的逻辑一样保留圆角图片缓存,清除原有非圆角图片缓存

字典深浅拷贝

NSMutableDictionary *myDic=[@{@"22":@"33"} mutableCopy];
NSMutableDictionary *otherDic=myDic;
//NSMutableDictionary *otherDic=[myDic mutableCopy];
[otherDic setValue:@"33" forKey:@"44"];

改变可变字典otherDic时myDic也会同时改变,所以使用可变字典时要让两个字典独立需要注意使用mutableCopy.

NSMutableSet里面尽量少用不可变对象

NSMutableSet *set=[NSMutableSet new];
NSMutableArray *arrayA=[@[@1,@2] mutableCopy];
[set addObject:arrayA];
NSLog(@"set=%@",set);
    
NSMutableArray *arrayB=[@[@1,@2] mutableCopy];
[set addObject:arrayB];
NSLog(@"set=%@",set);
    
NSMutableArray *arrayC=[@[@1] mutableCopy];
//[set addObject:[arrayC copy]];
[set addObject:arrayC];
NSLog(@"set=%@",set);
    
[arrayC addObject:@2];
NSLog(@"set=%@",set);
    
NSSet *setB=[set copy];
NSLog(@"setB=%@",setB);

如上面代码所示使用可变对象时会出现里面有相同元素的情况,而当重新将其浅拷贝的时候则里面内容会转回不可变对象,所以才会恢复正常.

打印输出黑科技

重写实体类如下方法然后就可以直接通过NSLog(@”cls=%@”,cls)输出定制的内容

- (NSString *)description {
    return [NSString stringWithFormat:@"<%@: %p, %@", [self class],self,@{@"youName":_youName,                                                                                             @"myName":_myName}];
}
//debug环境下
- (NSString *)debugDescription {
//    return [NSString stringWithFormat:@"<%@: %p, %@", [self class],self,@{@"youName":_youName,
//                                                                          @"myName":_myName}];
    return [self description];
}

基于运行期OC的Get方法和Set方法的实现

//动态方法解析函数
+(BOOL)resolveInstanceMethod:(SEL)sel{
    NSString *selectorString=NSStringFromSelector(sel);
    if ([selectorString hasPrefix:@"set"]) {
        class_addMethod(self, sel, (IMP)autoDictionarySetter, "v@:@");
    }else{
        class_addMethod(self, sel, (IMP)autoDictionaryGetter, "@@:");
    }
    return YES;
}

id autoDictionaryGetter(id self,SEL _cmd){
    EOCAutoDictionary *typeSelf=(EOCAutoDictionary *)self;
    NSMutableDictionary *backingStore=typeSelf.backingStore;
    NSString *key=NSStringFromSelector(_cmd);
    return [backingStore objectForKey:key];
}

void autoDictionarySetter(id self,SEL _cmd,id value){
    EOCAutoDictionary *typeSelf=(EOCAutoDictionary *)self;
    NSMutableDictionary *backingStore=typeSelf.backingStore;
    
    NSString *selectorString=NSStringFromSelector(_cmd);
    NSMutableString *key=[selectorString mutableCopy];
    
    [key deleteCharactersInRange:NSMakeRange(key.length - 1, 1)];
    
    [key deleteCharactersInRange:NSMakeRange(0, 3)];
    
    NSString *lowercaseFirstChar=[[key substringToIndex:1] lowercaseString];
    [key replaceCharactersInRange:NSMakeRange(0, 1) withString:lowercaseFirstChar];
    if (value) {
        [backingStore setObject:value forKey:key];
    }else{
        [backingStore removeObjectForKey:key];
    }
}

当对象在收到无法解读的消息后,首先调用其所属类的下列类方法

+(BOOL)resolveInstanceMethod:(SEL)sel

所以可以利用其消息转发机制的这个函数来重新get,set方法,完整代码链接.

valueForKeyPath使用总结

取数组里面数字的最大值

NSArray * array = [NSArray arrayWithObjects:@0,@50,@9, nil];
NSInteger max = [[array valueForKeyPath:@"@max.floatValue"] integerValue];
NSLog(@"%ld",(long)max);

去数组里面数字的平均值

NSArray *arr = @[@0,@10,@40];
CGFloat avg = [[arr valueForKeyPath:@"@avg.floatValue"] floatValue];
NSLog(@"---%f",avg);

剔除重复数据

NSArray *array1 = @[@"name", @"w", @"aa", @"jimsa", @"aa"];
NSLog(@"%@", [array1 valueForKeyPath:@"@distinctUnionOfObjects.self"]);

同样可以嵌套使用，先剔除name对应值的重复数据再取值

NSArray *array2 = @[@{@"name" : @"cookeee",@"code" : @1},
                       @{@"name": @"jim",@"code" : @2},
                       @{@"name": @"jim",@"code" : @1},
                       @{@"name": @"jbos",@"code" : @1}];
    
NSLog(@"%@", [array2 valueForKeyPath:@"@distinctUnionOfObjects.name"]);

执行数组里面的特定属性处理完成后返回一个数组

NSArray *arrayList = @[@"name", @"w", @"aa", @"jimsa"];
NSLog(@"%@", [arrayList valueForKeyPath:@"uppercaseString"]);

求和、求平均值、最大值、最小值

NSNumber *sum = [array valueForKeyPath:@"@sum.floatValue"];
NSNumber *avg = [array valueForKeyPath:@"@avg.floatValue"];
NSNumber *max = [array valueForKeyPath:@"@max.floatValue"];
NSNumber *min = [array valueForKeyPath:@"@min.floatValue"];

KVO

添加kvo通知

[self.dogName addObserver:self forKeyPath:@"masterName" options:NSKeyValueObservingOptionNew context:nil];

在实体类中设置通知

+(BOOL)automaticallyNotifiesObserversForKey:(NSString *)key{
    //自动通知
    if ([key isEqualToString:@"dogNameStr"]) {
        return YES;
    }
    //手动通知
    if ([key isEqualToString:@"masterName"]) {
        return NO;
    }
    return [super automaticallyNotifiesObserversForKey:key];
}

-(void)setMasterName:(NSString *)pmasterName{
    //设置手动通知
    [self willChangeValueForKey:@"masterName"];
    @synchronized(self) {
        _masterName=pmasterName;
    }
    [self didChangeValueForKey:@"masterName"];
}

然后在需要通知的界面接收通知

-(void)observeValueForKeyPath:(NSString *)keyPath ofObject:(id)object change:(NSDictionary<NSKeyValueChangeKey,id> *)change context:(void *)context{
    if ([object isKindOfClass:[clsDogName class]]) {
        if ([keyPath isEqualToString:@"dogNameStr"]) {
            self.lbDogName.text=[change objectForKey:NSKeyValueChangeNewKey];
        }
    }
}

主要用于比如在一个界面修改了用户的资料,按保存同时能实时的同步修改用户的资料这样类似的场景.

NSPredicate谓词筛选器

把时间小于2016-10-04的时候剔除,重复时间也剔除,然后排序,其他用法在这里

-(void)loadPredicateTest{
    //把DATETIME相同时间合并排序,然后再过滤掉2016-10-04号前的日期
    NSArray *list=@[@{@"DATETIME":@"2016-10-01"},
                    @{@"DATETIME":@"2016-10-06"},
                    @{@"DATETIME":@"2016-10-05"},
                    @{@"DATETIME":@"2016-10-04"},
                    @{@"DATETIME":@"2016-10-05"},
                    @{@"DATETIME":@"2016-10-03"},
                    @{@"DATETIME":@"2016-10-02"},
                    @{@"DATETIME":@"2016-10-02"}];
    
    //把日期过滤
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"DATETIME >= '2016-10-04'"];//创建谓词筛选器
    NSArray *filtrationList = [list filteredArrayUsingPredicate:predicate];
    //剔除重复数据
    filtrationList=[filtrationList valueForKeyPath:@"@distinctUnionOfObjects.DATETIME"];
    //排序
    NSArray *sortSetArray = [filtrationList sortedArrayUsingDescriptors:@[[NSSortDescriptor sortDescriptorWithKey:nil ascending:NO]]];
    NSLog(@"%@",sortSetArray);
}