李二狗 — @Meniny
Table of Content
介绍一些 iOS 小知识。
KVC 与简单集合运算
也就是 @sum、@avg、@count、@max、@min 这五个家伙，分别表示和、平均值、计数、最大值，最小值。
举个栗子:
NSArray *array = [NSArray arrayWithObjects:@"1.0", @(2.0), @(3.4), @(4.5), @10, nil];
CGFloat sum = [[array valueForKeyPath:@"@sum.doubleValue"] doubleValue];
NSLog(@"sum = %lf", sum);
CGFloat avg = [[array valueForKeyPath:@"@avg.doubleValue"] doubleValue];
NSLog(@"avg = %lf", avg);
CGFloat max =[[array valueForKeyPath:@"@max.doubleValue"] doubleValue];
NSLog(@"max = %lf", max);
CGFloat min =[[array valueForKeyPath:@"@min.doubleValue"] doubleValue];
NSLog(@"min = %lf", min);
再举个栗子:
#import <Foundation/Foundation.h>
@interface Thing: NSObject
@property (nonatomic, assign) NSUInteger serial;
@end
@implementation Thing
- (instancetype)initWithSerial:(NSUInteger)serial {
self = [super init];
if (self) {
self.serial = serial;
}
return self;
}
@end
int main(int argc, char *argv[]) {
@autoreleasepool {
NSArray *array = @[
[[Thing alloc] initWithSerial:1],
[[Thing alloc] initWithSerial:2],
[[Thing alloc] initWithSerial:3],
[[Thing alloc] initWithSerial:4],
[[Thing alloc] initWithSerial:5],
];
NSNumber* sum = [array valueForKeyPath:@"@sum.serial"];
NSLog(@"sum = %zd", sum.unsignedIntegerValue);
NSNumber* avg = [array valueForKeyPath:@"@avg.serial"];
NSLog(@"avg = %zd", avg.unsignedIntegerValue);
NSNumber* min = [array valueForKeyPath:@"@min.serial"];
NSLog(@"min = %zd", min.unsignedIntegerValue);
NSNumber* max = [array valueForKeyPath:@"@max.serial"];
NSLog(@"max = %zd", max.unsignedIntegerValue);
NSNumber* count = [array valueForKeyPath:@"@count"];
NSLog(@"count = %zd", count.unsignedIntegerValue);
}
}
