iOS 给字典中插入nil的几种情景

NSString *str = nil;

NSDictionary *dic = @{@"key":str};

//zs20171220 会崩溃'*** -[__NSPlaceholderDictionary initWithObjects:forKeys:count:]: attempt to insert nil object from objects[0]

字面量添加nil 会崩溃

NSString *str = nil;

NSDictionary *dicParam = [[NSDictionary alloc] initWithObjectsAndKeys:@"",@"key1",str,@"key2",nil];

NSLog(@"dicParam____%@",dicParam[@"key2"]);//zs20171220 value 值可以为nil，但是这个时候nil意味着结束添加了

NSLog(@"dicParam____%@",dicParam.allKeys); NSLog(@"dicParam____%@",dicParam[@"key1"]);//zs20171220 key 不能设置成nil 否则会崩溃

NSString *str = nil;

NSMutableDictionary *dicMutable = [NSMutableDictionary dictionaryWithCapacity:0];

[dicMutable setValue:str forKey:@"key1"];//zs20171220 插入nil 不会崩溃

[dicMutable setValue:@"ddd" forKey:@"key2"];

[dicMutable setValue:nil forKey:@"key3"];//zs20171220 插入nil 不会有这个key 和值

NSLog(@"___%@",dicMutable);