本文主要是介绍iOS之NSDictionary使用集合和各种为空判断，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
========JSON字符串转换成字典========
NSData *jsonData = [jsonString dataUsingEncoding:NSUTF8StringEncoding]; NSError *err; NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:jsonData options:NSJSONReadingMutableContainers error:&err];=========判断字典内容是否为空=======
NSDictionary *dic=[[NSDictionaryalloc]init];
if(dic.count==0 ){
NSLog(@"字典为空02");
}
NSDictionary *dict;
NSLog(@"字典---%@",dict);
if (!dict) {
NSLog(@"字典为空");
}else {
NSLog(@"字典不为空");
}
NSDictionary *dict;
NSLog(@"字典---%@",dict);
if (![dictcount]) {
NSLog(@"字典为空");//
}else {
NSLog(@"字典不为空");
}
========判断字典包含某个key===
方法一：
NSDictionary *dict=@{@"key":@""
};
NSLog(@"字典---%@",dict);
if(![[dictallKeys]containsObject:@"key"]){
NSLog(@"键值为空");
}else {
NSLog(@"键值不为空");/
}
方法二：NSDictionary *dict=@{
@"s":@{@"a":@"ax"
}
};
NSLog(@"字典---%@",dict);
if (!dict[@"q"]) {
NSLog(@"字典键不存在");//
}else {
NSLog(@"字典键存在");
}
============
在APP开发过程中，我们有时候要从服务器加载数据时，一般是都是用json或者xml解析后用NSDictionary保存，但是从服务器加载过来的数据直接使用时会崩溃，是因为在NSDictionary中的某个值为<null>或者NSnull ，但是我们用一般的检查根本检查不出来，如if( [obc objectForKey:key]==nil) 没有效果，这时候就要对NSDictionary的中值做处理了，把NSDictionary中值为<null>或者NSnull替换成@""就行了，上函数：
- (id) processDictionaryIsNSNull:(id)obj{
const NSString *blank = @"";
if ([obj isKindOfClass:[NSDictionary class]]) {
NSMutableDictionary *dt = [(NSMutableDictionary*)obj mutableCopy];
for(NSString *key in [dt allKeys]) {
id object = [dt objectForKey:key];
if([object isKindOfClass:[NSNull class]]) {
[dt setObject:blank
forKey:key];
}
else if ([object isKindOfClass:[NSString class]]){
NSString *strobj = (NSString*)object;
if ([strobj isEqualToString:@"<null>"]) {
[dt setObject:blank
forKey:key];
}
}
else if ([object isKindOfClass:[NSArray class]]){
NSArray *da = (NSArray*)object;
da = [self processDictionaryIsNSNull:da];
[dt setObject:da
forKey:key];
}
else if ([object isKindOfClass:[NSDictionary class]]){
NSDictionary *ddc = (NSDictionary*)object;
ddc = [self processDictionaryIsNSNull:object];
[dt setObject:ddc forKey:key];
}
}
return [dt copy];
}
else if ([obj isKindOfClass:[NSArray class]]){
NSMutableArray *da = [(NSMutableArray*)obj mutableCopy];
for (int i=0; i<[da count]; i++) {
NSDictionary *dc = [obj objectAtIndex:i];
dc = [self processDictionaryIsNSNull:dc];
[da replaceObjectAtIndex:i withObject:dc];
}
return [da copy];
}
else{
return obj;
}
}
====================================@property(nonatomic,strong)NSMutableArray *muarr;
@property(nonatomic,copy)NSString *str;
@property(nonatomic,strong)NSDictionary *dict;
@property(nonatomic,copy)void(^block)(int x);
NSLog(@"--arr--%@,--str---%@--,dict---%@--,self.block---%@",self.muarr,self.str,self.dict,self.block);
if(!self.muarr){
NSLog(@"数组nil");
}
if(self.muarr.count==0){
NSLog(@"空数组");
}
if(!self.str){
NSLog(@"字符串nil");
}
if([self.strisEqualToString:@""]){
NSLog(@"空字符串");
}
if(!self.dict){
NSLog(@"字典nil");
}
if(self.dict.count==0){
NSLog(@"空字典");
}
if(!self.block){
NSLog(@"block ---nil");
}
结果：
2018-01-17 08:53:08.018374+0800 FastApps[19950:1346083] --arr--(null),--str---(null)--,dict---(null)--,self.block---(null)
2018-01-17 08:53:08.018495+0800 FastApps[19950:1346083] 数组nil
2018-01-17 08:53:08.018602+0800 FastApps[19950:1346083] 空数组
2018-01-17 08:53:08.018659+0800 FastApps[19950:1346083] 字符串nil
2018-01-17 08:53:08.018706+0800 FastApps[19950:1346083] 字典nil
2018-01-17 08:53:08.018765+0800 FastApps[19950:1346083] 空字典
2018-01-17 08:53:08.018839+0800 FastApps[19950:1346083] block ---nil
后台返回的字段"bank_card" = "<null>";-------如果是用字典去值，则结果是字符串"<null>"
，如果用mjextention字典转模型后去取值，则转换成nil；这篇关于iOS之NSDictionary使用集合和各种为空判断的文章就介绍到这儿，希望我们推荐的文章对编程师们有所帮助！
