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对象集合 一
1，创建数组。
NSArray是固定数组，NSMutableArray是可变数组。
创建固定数组
NSArray *listOfLetters = [NSArray arrayWithObjects:@"A", @"B", @"C", nil];
也可用类似的方法创建可变数组，NSMutableArray是NSArray的子类。下面是一些最常用的方法以及解释。
- (id)initWithObjects:(const id [])objects count:(NSUInteger)cnt; Initializes an array with the specified objects and count
- (id)initWithObjects:(id)firstObj, ...
NS_REQUIRES_NIL_TERMINATION;
Initializes an array with the specified nil- terminated list of objects
- (id)initWithArray:(NSArray *)array;
Initializes an array using another array
- (id)initWithArray:(NSArray *)array copyItems:(BOOL)flag;
Initializes an array using another array and creates new copies of each object
- (id)initWithContentsOfFile:(NSString *)path;
Initializes an array with the contents of a local file
- (id)initWithContentsOfURL:(NSURL *)url;
Initializes an array with the contents at a URL
代码例子。
//创建打印固定数组。
NSArray *listOfLetters1 = [NSArray arrayWithObjects:@"A", @"B", @"C", nil];
NSLog(@"listOfLetters1 = %@", listOfLetters1);
//这里注意NSNumber是对象
NSNumber *number1 = [NSNumber numberWithInt:1];
NSNumber *number2 = [NSNumber numberWithInt:2];
NSNumber *number3 = [NSNumber numberWithInt:3];
NSMutableArray *listOfNumbers1 = [[NSMutableArray alloc] initWithObjects:number1, number2, number3, nil];
NSLog(@"listOfNumbers1 = %@", listOfNumbers1);
//极少用的方法
id list[3];
list[0] = @"D";
list[1] = @"E";
list[2] = @"F”;
//这里给分配了数组的长度。
NSMutableArray *listOfLetters2 = [[NSMutableArray alloc] initWithObjects:list count:3];
NSLog(@"listOfLetters2 = %@", listOfLetters2);
2，数组引用对象。
得到数组内的第一个对象
NSString *stringObject1 = [listOfLetters objectAtIndex:0];
得到数组内最后一个对象
NSString *stringObject2 = [listOfLetters lastObject];
你也可以通过内容找到数组的下标
NSUInteger position = [listOfLetters indexOfObject:@"B”];
具体代码
NSMutableArray *listOfLetters = [NSMutableArray arrayWithObjects:@"A", @"B", @"C", nil];
NSString *stringObject1 = [listOfLetters objectAtIndex:0];
NSLog(@"stringObject1 = %@", stringObject1);
NSString *stringObject2 = [listOfLetters lastObject];
NSLog(@"stringObject2 = %@", stringObject2);
NSUInteger position = [listOfLetters indexOfObject:@"B"];
NSLog(@"position = %lu", position);
3，获取数组个数。
用数组.count就可以，
具体代码例子。
NSMutableArray *listOfLetters = [NSMutableArray arrayWithObjects:@"A", @"B", @"C", nil];
NSLog(@"listOfLetters has %lu elements", listOfLetters.count);
4，遍历数组
我们就不用书上的方法了，这里直接创建数组。
NSArray *listOfObjects = @[@"A",@"B",@"C",@"D”];
然后遍历它。
for(NSMutableString *s in listOfObjects){
NSLog(@"This string in lowercase is %@", [s lowercaseString]);
}
这里 用lowercaseString把字符串变小写了。
也可以用@selector向数组发送方法，用withObject来传递参数
[listOfObjects makeObjectsPerformSelector:@selector(appendString:)
withObject:@"-MORE”];
需要确认方法appendString可用。
利用blocks遍历数组。
[listOfObjects enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop)
{
NSLog(@"object(%lu)‘s description is %@",idx, [obj description]);
}];
具体代码例子
NSMutableString *string1 = [NSMutableString stringWithString:@"A"];
NSMutableString *string2 = [NSMutableString stringWithString:@"B"];
NSMutableString *string3 = [NSMutableString stringWithString:@"C"];
// NSArray *listOfObjects = [NSArray arrayWithObjects:string1, string2, string3, nil];
// 这里string1 等必须是可变字符串，写死是不行的 appendString方法会报错。
NSArray *listOfObjects = @[string1, string2, string3];
for(NSMutableString *s in listOfObjects){
NSLog(@"This string in lowercase is %@", [s lowercaseString]);
}
[listOfObjects makeObjectsPerformSelector:@selector(appendString:)
withObject:@"-MORE"];
[listOfObjects enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) {
NSLog(@"object(%lu)‘s description is %@",idx, [obj description]);
}];
5，数组排序。
创建Person类，然后创建数组。
person类大概是这个样子，.h文件
#import <Foundation/Foundation.h>
@interface Person : NSObject
@property(strong) NSString *firstName;
@property(strong) NSString *lastName;
@property(assign) int age;
-(id)initWithFirstName:(NSString *)fName lastName:(NSString *)lName andAge:(int)a;
-(void)reportState;
@end
Person.m
#import "Person.h"
@implementation Person
@synthesize firstName, lastName, age;
-(id)initWithFirstName:(NSString *)fName lastName:(NSString *)lName andAge:(int)a{
self = [super init];
if (self) {
self.firstName = fName;
self.lastName = lName;
self.age = a;
}
return self;
}
-(void)reportState{
NSLog(@"This person‘s name is %@ %@ who is %i years old", firstName, lastName, age);
}
@end
创建数组
//Instantiate Person objects and add them all to an array:
Person *p1 = [[Person alloc] initWithFirstName:@"Rebecca"
lastName:@"Smith"
andAge:33];
Person *p2 = [[Person alloc] initWithFirstName:@"Albert"
lastName:@"Case"
andAge:24];
Person *p3 = [[Person alloc] initWithFirstName:@"Anton"
lastName:@"Belfey"
andAge:45];
Person *p4 = [[Person alloc] initWithFirstName:@"Tom"
lastName:@"Gun"
andAge:17];
Person *p5 = [[Person alloc] initWithFirstName:@"Cindy"
lastName:@"Lou"
andAge:6];
Person *p6 = [[Person alloc] initWithFirstName:@"Yanno"
lastName:@"Dirst"
andAge:76];
NSArray *listOfObjects = [NSArray arrayWithObjects:p1, p2, p3, p4, p5, p6, nil];
可以使用NSSortDescriptor排序，例如
//Create three sort descriptors and add to an array:
NSSortDescriptor *sd1 = [NSSortDescriptor sortDescriptorWithKey:@"age"
ascending:YES];
NSSortDescriptor *sd2 = [NSSortDescriptor sortDescriptorWithKey:@"lastName"
ascending:YES];
NSSortDescriptor *sd3 = [NSSortDescriptor sortDescriptorWithKey:@"firstName"
ascending:YES];
NSArray *sdArray1 = [NSArray arrayWithObjects:sd1, sd2, sd3, nil];
传入你要排序的字段和是否正序排列。
通过描述符对数组进行排序。
NSArray *sortedArray1 = [listOfObjects sortedArrayUsingDescriptors:sdArray1];
注意，sdArray1。
具体代码示例。
@autoreleasepool {
//Instantiate Person objects and add them all to an array:
Person *p1 = [[Person alloc] initWithFirstName:@"Rebecca"
lastName:@"Smith"
andAge:33];
Person *p2 = [[Person alloc] initWithFirstName:@"Albert"
lastName:@"Case"
andAge:24];
Person *p3 = [[Person alloc] initWithFirstName:@"Anton"
lastName:@"Belfey"
andAge:45];
Person *p4 = [[Person alloc] initWithFirstName:@"Tom"
lastName:@"Gun"
andAge:17];
Person *p5 = [[Person alloc] initWithFirstName:@"Cindy"
lastName:@"Lou"
andAge:6];
Person *p6 = [[Person alloc] initWithFirstName:@"Yanno"
lastName:@"Dirst"
andAge:76];
NSArray *listOfObjects = [NSArray arrayWithObjects:p1, p2, p3, p4, p5, p6, nil];
NSLog(@"PRINT OUT ARRAY UNSORTED");
[listOfObjects makeObjectsPerformSelector:@selector(reportState)];
//Create three sort descriptors and add to an array:
NSSortDescriptor *sd1 = [NSSortDescriptor sortDescriptorWithKey:@"age"
ascending:YES];
NSSortDescriptor *sd2 = [NSSortDescriptor sortDescriptorWithKey:@"lastName"
ascending:YES];
NSSortDescriptor *sd3 = [NSSortDescriptor sortDescriptorWithKey:@"firstName"
ascending:YES];
NSArray *sdArray1 = [NSArray arrayWithObjects:sd1, sd2, sd3, nil];
NSLog(@"PRINT OUT SORTED ARRAY (AGE,LASTNAME,FIRSTNAME)");
NSArray *sortedArray1 = [listOfObjects sortedArrayUsingDescriptors:sdArray1];
[sortedArray1 makeObjectsPerformSelector:@selector(reportState)];
NSArray *sdArray2 = [NSArray arrayWithObjects:sd2, sd1, sd3, nil];
NSArray *sortedArray2 = [listOfObjects sortedArrayUsingDescriptors:sdArray2];
NSLog(@"PRINT OUT SORTED ARRAY (LASTNAME,FIRSTNAME,AGE)");
[sortedArray2 makeObjectsPerformSelector:@selector(reportState)];
}
6，数组查询。
一旦有你的谓词设置，可利用filteredArrayUsingPredicate获取查询值，并发送谓词作为参数。
例如
NSArray *arraySubset = [listOfObjects filteredArrayUsingPredicate:predicate];
Person类不变，看main里的代码。
@autoreleasepool {
//Instantiate Person objects and add them all to an array:
Person *p1 = [[Person alloc] initWithFirstName:@"Rebecca"
lastName:@"Smith"
andAge:33];
Person *p2 = [[Person alloc] initWithFirstName:@"Albert"
lastName:@"Case"
andAge:24];
Person *p3 = [[Person alloc] initWithFirstName:@"Anton"
lastName:@"Belfey"
andAge:45];
Person *p4 = [[Person alloc] initWithFirstName:@"Tom"
lastName:@"Gun"
andAge:17];
Person *p5 = [[Person alloc] initWithFirstName:@"Cindy"
lastName:@"Lou"
andAge:6];
Person *p6 = [[Person alloc] initWithFirstName:@"Yanno"
lastName:@"Dirst"
andAge:76];
NSArray *listOfObjects = [NSArray arrayWithObjects:p1, p2, p3, p4, p5, p6, nil];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"age > 30"];
NSArray *arraySubset = [listOfObjects filteredArrayUsingPredicate:predicate];
NSLog(@"PRINT OUT ARRAY SUBSET");
[arraySubset makeObjectsPerformSelector:@selector(reportState)];
}
7，操纵数组内容。就是一堆现成的方法，本别是给数组插入值，insertObject，前端插入，指定位置替换值replaceObjectAtIndex，更改位置，exchangeObjectAtIndex，根据下标和内容移除值，移除第一个值，移除最后一个值，移除所有值。
代码示例
NSMutableArray *listOfLetters = [[NSMutableArray alloc] init];
[listOfLetters addObject:@"A"];
[listOfLetters addObject:@"B"];
[listOfLetters addObject:@"C"];
NSLog(@"OBJECTS ADDED TO ARRAY: %@", listOfLetters);
[listOfLetters insertObject:@"a"
atIndex:0];
NSLog(@"OBJECT ‘a‘ INSERTED INTO ARRAY: %@", listOfLetters);
[listOfLetters replaceObjectAtIndex:2
withObject:@"c"];
NSLog(@"OBJECT ‘c‘ REPLACED ‘C‘ IN ARRAY: %@", listOfLetters);
[listOfLetters exchangeObjectAtIndex:0
withObjectAtIndex:2];
NSLog(@"OBJECT AT INDEX 1 EXCHANGED WITH OBJECT AT INDEX 2 IN ARRAY: %@", listOfLetters);
[listOfLetters removeObject:@"A"];
NSLog(@"OBJECT ‘A‘ REMOVED IN ARRAY: %@", listOfLetters);
[listOfLetters removeObjectAtIndex:1];
NSLog(@"OBJECT AT INDEX 1 REMOVED IN ARRAY: %@", listOfLetters);
[listOfLetters removeLastObject];
NSLog(@"LAST OBJECT REMOVED IN ARRAY: %@", listOfLetters);
[listOfLetters removeAllObjects];
NSLog(@"ALL OBJECTS REMOVED IN ARRAY: %@", listOfLetters);
8，将数组值写入文件。
NSArray *listOfObjects = [NSArray arrayWithObjects:@"A", @"B", @"C", [NSNumber numberWithInt:1], [NSNumber numberWithInt:2], [NSNumber numberWithInt:3], nil];
NSString *filePathName = @"/Users/Shared/array.txt";
[listOfObjects writeToFile:filePathName
atomically:YES];
我们看到array.txt虽然是txt文件，但写入的数组是xml格式的。
9，从文件读取内容。紧接着上段代码，我们看到我们读取出来的是一个数组。
NSString *filePathName = @"/Users/Shared/array.txt";
NSArray *listOfObjects = [[NSArray alloc] initWithContentsOfFile:filePathName];
NSLog(@"%@", listOfObjects);