iOS：为什么我不能将nil设置为NSDictionary值？ [英] iOS: Why can't I set nil to NSDictionary value?

问题描述

这可能是一个非常基本的问题，但我想知道为什么我不能将nil指定为NSDictionary值？我在我的代码中有很多地方。如果 [q objectForKey：@text] 为nil，则App崩溃。

This might be very basic question but I was wondering why can't I assign nil as NSDictionary value? I have following statement many places in my code. If [q objectForKey:@"text"] is nil then App is crashing.

NSMutableDictionary *dict = [[NSMutableDictionary alloc] initWithCapacity:2];
[dict setObject:[q objectForKey:@"text"] forKey:@"text"];

在将字符分配给字典之前，我必须在每个地方检查nil。这是唯一正确的做法吗？我错过了一些明显的东西吗

I have to check everywhere for the nil before assigning it to dictionary. Is this the only correct way of doing? Am I missing something obvious?

if([q objectForKey:@"text"] != nil)
    [dict setObject:[q objectForKey:@"text"] forKey:@"text"];
else
    [dict setObject:@"" forKey:@"text"];

推荐答案

它想要一个实际的对象...使用 NSNull

It wants an actual object... use NSNull

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