我使用iOS7 Xcode 5与Parse.com的SDK。在通过解析查询数据时，我试图为每个返回的对象构建一个Person (NSObject)，并创建一个defaultPeople的NSArray。下面是Person的代码:
Person.h
// Person.h
#import <Foundation/Foundation.h>
@interface Person : NSObject
@property (nonatomic, strong) NSString *name;
@property (nonatomic, strong) UIImage *image;
@property (nonatomic, assign) NSUInteger age;
@property (nonatomic, strong) NSString *gender;
@property (nonatomic, strong) NSString *location;
@property (nonatomic, strong) NSString *tagline;
@property (nonatomic, strong) NSString *objectId;
- (instancetype)initWithName:(NSString *)name
image:(UIImage *)image
age:(NSUInteger)age
gender:(NSString*)gender
location:(NSString*)location
tagline:(NSString*)tagline
objectId:(NSString*)objectId;
@end
Person.m:
// Person.m
#import "Person.h"
@implementation Person
#pragma mark - Object Lifecycle
- (instancetype)initWithName:(NSString *)name
image:(UIImage *)image
age:(NSUInteger)age
gender:(NSString*)gender
location:(NSString *)location
tagline:(NSString*)tagline
objectId:(NSString *)objectId {
self = [super init];
if (self) {
_name = name;
_image = image;
_age = age;
_gender = gender;
_location = location;
_tagline = tagline;
_objectId = objectId;
}
return self;
}
@end
下面是我用来在视图控制器。m文件中创建数组的代码:
- (NSArray *)defaultPeople {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSLog(@"Current City for Querying: %@", [defaults objectForKey:@"CurrentCity"]);
if ([defaults objectForKey:@"CurrentCity"]) {
PFQuery *query = [PFQuery queryWithClassName:@"_User"];
[query whereKey:@"CurrentCity" equalTo:[defaults objectForKey:@"CurrentCity"]];
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (!error) {
// The find succeeded.
NSLog(@"Successfully retrieved %d scores.", objects.count);
// Do something with the found objects
for (PFObject *object in objects) {
NSString *userID = object.objectId;
NSString *first = [object objectForKey:@"FirstName"];
NSString *city = [object objectForKey:@"CurrentCity"];
NSUInteger age = (int)[object objectForKey:@"Age"];
NSString *gender = [object objectForKey:@"Gender"];
NSString *tagline = [object objectForKey:@"Tagline"];
Person *p = [[Person alloc]
initWithName:first
image:[UIImage imageWithData:
[NSData dataWithContentsOfURL:
[NSURL URLWithString:
[object objectForKey:@"PictureURL"]]]]
age:age
gender:gender
location:city
tagline:tagline
objectId:userID];
[self.people addObject:p]
}
} else {
NSLog(@"Error: %@ %@", error, [error userInfo]);
}
}];
}
return self.people; //people was defined in the interface as:
//@property (nonatomic, strong) NSMutableArray *people;
}
我知道查询是好的，因为我在for循环中nsloging了每个NSString/NSUInteger，它总是返回正确的值。我的问题是从这些值创建一个新的Person对象，并在每次迭代后将其添加到defaultPeople数组。这段代码的结果是我的defaultPeople数组总是返回(null)。请帮助! !谢谢:)
克莱顿好了，伙计们，最后我弄清楚了如何在一个实际工作的块中做到这一点:
- (void)queryForAllPostsNearLocation:(CLLocation *)currentLocation withNearbyDistance:(CLLocationAccuracy)nearbyDistance {
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setBool:1 forKey:@"Users"];
PFQuery *query = [PFQuery queryWithClassName:@"_User"];
// If no objects are loaded in memory, we look to the cache first to fill the table
// and then subsequently do a query against the network.
if (query.countObjects == 0) {
query.cachePolicy = kPFCachePolicyCacheThenNetwork;
}
// Create a PFGeoPoint using the current location (to use in our query)
PFGeoPoint *userLocation =
[PFGeoPoint geoPointWithLatitude:[Global shared].LastLocation.latitude longitude:[Global shared].LastLocation.longitude];
// Create a PFQuery asking for all wall posts 1km of the user
[query whereKey:@"CurrentCityCoordinates" nearGeoPoint:userLocation withinKilometers:10];
// Include the associated PFUser objects in the returned data
[query includeKey:@"objectId"];
//Run the query in background with completion block
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
if (error) { // The query failed
NSLog(@"Error in geo query!");
} else { // The query is successful
defaultPeople = [[NSMutableArray alloc] init];
// 1. Find new posts (those that we did not already have)
// In this array we'll store the posts returned by the query
NSMutableArray *people = [[NSMutableArray alloc] initWithCapacity:100];
// Loop through all returned PFObjects
for (PFObject *object in objects) {
// Create an object of type Person with the PFObject
Person *p = [[Person alloc] init];
NSString *userID = object.objectId;
p.objectId = userID;
NSString *first = [object objectForKey:@"FirstName"];
p.name = first;
NSString *city = [object objectForKey:@"CurrentCity"];
p.location = city;
NSString *age = [object objectForKey:@"Age"];
p.age = age;
NSString *gender = [object objectForKey:@"Gender"];
p.gender = gender;
NSString *tagline = [object objectForKey:@"Tagline"];
p.tagline = tagline;
UIImage *img = [UIImage imageWithData:[NSData dataWithContentsOfURL:[NSURL URLWithString:[NSString stringWithFormat:@"%@",[object objectForKey:@"PictureURL"]]]]];
p.image = img;
if (![p.objectId isEqualToString:myID] && ![p.gender isEqualToString:myGender] && ![people containsObject:p]) {
[people addObject:p];
NSLog(@"Person: %@",p);
}
}
[defaultPeople addObjectsFromArray:people];
[[Global shared] setDefaultPeople:defaultPeople];
NSLog(@"Default People: %@",[Global shared].defaultPeople);
NSLog(@"Success. Retrieved %lu objects.", (unsigned long)[Global shared].defaultPeople.count);
if (defaultPeople.count == 0) {
[defaults setBool:0 forKey:@"Users"];
} else {
[defaults setBool:1 forKey:@"Users"];
}
}
}];
}
底部的BOOL返回值是让控制器知道是否在提示时切换视图控制器。如果开关控制器开关被击中，它只在BOOL = 1时切换，即该区域有人。
谢谢你们的帮助。认真。
[self。people addObject:p]发生在后台线程中所以"return self。人"发生在自我之前"。人是更新的。这就是为什么它总是返回nil。
而不是[query findObjectsInBackground]NSArray *objects = [query findObjects]
您需要返回块内的人员，否则它将在完成查找对象之前击中返回语句。它与block异步查找它们
另一种方法是去掉该块并执行:
NSArray *array = [query findObjects];
for (PFObject *object in array) {
NSString *userID = object.objectId;
NSString *first = [object objectForKey:@"FirstName"];
NSString *city = [object objectForKey:@"CurrentCity"];
NSUInteger age = (int)[object objectForKey:@"Age"];
NSString *gender = [object objectForKey:@"Gender"];
NSString *tagline = [object objectForKey:@"Tagline"];
Person *p = [[Person alloc]
initWithName:first
image:[UIImage imageWithData:
[NSData dataWithContentsOfURL:
[NSURL URLWithString:
[object objectForKey:@"PictureURL"]]]]
age:age
gender:gender
location:city
tagline:tagline
objectId:userID];
[self.people addObject:p];
}
return self.people;