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()

}