nsnull

What's the difference between [NSNull null] and nil?

由 Deadly 提交于 2019-11-27 03:48:59
Here's a context where I have seen that: NSMutableArray *controllers = [[NSMutableArray alloc] init]; for (unsigned i = 0; i < kNumberOfPages; i++) { [controllers addObject:[NSNull null]]; } why not nil in that place? Mike Caron Directly from Apple : The NSNull class defines a singleton object you use to represent null values in situations where nil is prohibited as a value (typically in a collection object such as an array or a dictionary). So in your example, that's exactly what's happening, the programmer is choosing to put a null object into the controllers array, where nil is not allowed

Replace all NSNull objects in an NSDictionary

由 ≯℡__Kan透↙ 提交于 2019-11-27 03:28:42
I'm curious, I currently have an NSDictionary where some values are set to an NSNull object thanks to the help of json-framework. The aim is to strip all NSNull values and replace it with an empty string. I'm sure someone has done this somewhere? No doubt it is probably a four liner and is simple, I am just far too burnt out to figure this out on my own. Thanks! Really simple: @interface NSDictionary (JRAdditions) - (NSDictionary *)dictionaryByReplacingNullsWithStrings; @end @implementation NSDictionary (JRAdditions) - (NSDictionary *)dictionaryByReplacingNullsWithStrings { const

How to detect if NSString is null?

由 喜你入骨 提交于 2019-11-27 02:41:59
I have a piece of code that detects if a NSString is NULL , nil , etc. However, it crashes. Here is my code: NSArray *resultstwo = [database executeQuery:@"SELECT * FROM processes WHERE ready='yes' LIMIT 0,1"]; for (NSDictionary *rowtwo in resultstwo) { NSString *getCaption = [rowtwo valueForKey:@"caption"]; if (getCaption == NULL) { theCaption = @"Photo uploaded..."; } else if (getCaption == nil) { theCaption = @"Photo uploaded..."; } else if ([getCaption isEqualToString:@""]) { theCaption = @"Photo uploaded..."; } else if ([getCaption isEqualToString:@" "]) { theCaption = @"Photo uploaded...

What is causing NSNull length unrecognized selector keyCommand error

由 依然范特西╮ 提交于 2019-11-26 18:28:55
问题 I have this class/storyboard scene in a project that up to last night worked fine for the past 4 weeks i worked on it. I have managed to comment out practically everything and I still get the crash when tapping on the UITextField and typing a number. It only crashes when I type in a value, otherwise it doesn't crash. Here is the class as I am running it now: import Foundation import UIKit import HealthKit import CoreData class WorkoutViewController: UITableViewController { //Properties

Difference between nil, NIL and, null in Objective-C

由 假如想象 提交于 2019-11-26 18:11:51
I want to know the difference between nil , NIL and null . I've googled around and found this: nil -> null pointer to Objective-C object NIL -> null pointer to Objective-C class null -> null pointer to primitive type or absence of data But I'm not able to understand the terms "Objective-C object" and "class" clearly. Please explain this to me. Also, is there any word like NSNull or NSNil in Objective-C? If so, then please explain for what it is for. nil is the literal null value for Objective-C objects, corresponding to the abstract type id or any Objective-C type declared via @interface . For

Detect a Null value in NSDictionary

由 青春壹個敷衍的年華 提交于 2019-11-26 17:45:05
问题 I have an NSDictionary that's populated from a JSON response from an API server. Sometimes the values for a key in this dictionary are Null I am trying to take the given value and drop it into the detail text of a table cell for display. The problem is that when I try to coerce the value into an NSString I get a crash, which I think is because I'm trying to coerce Null into a string. What's the right way to do this? What I want to do is something like this: cell.detailTextLabel.text = sensor

Replace occurrences of NSNull in nested NSDictionary

由 我的未来我决定 提交于 2019-11-26 14:37:11
问题 This question is similar to this question, however this method only works on the root level of the dictionary. I'm looking to replace any occurrence of NSNull values with an empty string, so that I can save the full dictionary to a plist file (if i add it with the NSNull's the file won't write). My dictionary, however, has nested dictionaries inside it. Like this: "dictKeyName" = { innerStrKeyName = "This is a string in a dictionary"; innerNullKeyName = "<null>"; innerDictKeyName = {

How to detect if NSString is null?

由 南笙酒味 提交于 2019-11-26 12:34:57
问题 I have a piece of code that detects if a NSString is NULL , nil , etc. However, it crashes. Here is my code: NSArray *resultstwo = [database executeQuery:@\"SELECT * FROM processes WHERE ready=\'yes\' LIMIT 0,1\"]; for (NSDictionary *rowtwo in resultstwo) { NSString *getCaption = [rowtwo valueForKey:@\"caption\"]; if (getCaption == NULL) { theCaption = @\"Photo uploaded...\"; } else if (getCaption == nil) { theCaption = @\"Photo uploaded...\"; } else if ([getCaption isEqualToString:@\"\"]) {

Replace all NSNull objects in an NSDictionary

由 徘徊边缘 提交于 2019-11-26 10:29:39
问题 I\'m curious, I currently have an NSDictionary where some values are set to an NSNull object thanks to the help of json-framework. The aim is to strip all NSNull values and replace it with an empty string. I\'m sure someone has done this somewhere? No doubt it is probably a four liner and is simple, I am just far too burnt out to figure this out on my own. Thanks! 回答1: Really simple: @interface NSDictionary (JRAdditions) - (NSDictionary *)dictionaryByReplacingNullsWithStrings; @end

Difference between nil, NIL and, null in Objective-C

由 拥有回忆 提交于 2019-11-26 06:12:57
问题 I want to know the difference between nil , NIL and null . I\'ve googled around and found this: nil -> null pointer to Objective-C object NIL -> null pointer to Objective-C class null -> null pointer to primitive type or absence of data But I\'m not able to understand the terms \"Objective-C object\" and \"class\" clearly. Please explain this to me. Also, is there any word like NSNull or NSNil in Objective-C? If so, then please explain for what it is for. 回答1: nil is the literal null value
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