swift单例&OC单例

OC单例

#import "NetworkTools.h"

@implementation NetworkTools

+ (instancetype)sharedTools {
static NetworkTools *instance = nil;
static dispatch_once_t onceToken;
dispatch_once(&onceToken, ^{
instance = [[NetworkTools alloc] init];
});

return instance;
}
@end

swift单例

import UIKit

class SoundTools: NSObject {

//let 不可变 同样是线程安全的

static let tools: SoundTools = SoundTools()

}