IOS_OC_ Basic Syntax

1.YES and no

OBJECT-C provides a bool type, but this bool type is not the same as in C + +: everything in C + + that is not 0 value is true, and the value of 0 is false. But Object-c 1 is true and is defined by the macro as yes=1,0 false and defined by the macro as no=0.

+ (BOOL) isequals: (int) x with: (int) y{    return x-y;} if ([Provider isequals:10 with:1021]) {//= = YES//error        NSLog (@ "!!!!!!");} else {        NSLog (@ "=====");}

2. Class

In a class of OC, it is not allowed to define a function repeatedly, whether the function is repeated according to the method name, regardless of the receive parameter. Different from Java

pubic void GetInfo (Animal a);p ublic void GetInfo (person P);

The same method getinfo:-(void) GetInfo: (Animal) a;-(void) GetInfo: (person) p;

3. Common Collections

void    Arraytest () {Nsarray *array = [Nsarray arraywithobjects:@ "one", @ "one", @ "three", nil];    NSLog (@ "len =%lu", [array Count]);    For (NSObject *obj in array) {NSLog (@ "= =%@", obj);    } for (int i=0; I<[array count]; i++) {NSLog (@ "%@", [array objectatindex:i]);    }//write into the file, atomically whether to save the file to a temporary file, after the successful save, and then replace with the original file, is a security mechanism.    [Array writetofile:@ "/users/zf/desktop/1.txt" atomically:yes];    Read file Nsarray *arr = [Nsarray arraywithcontentsoffile:@ "/users/zf/desktop/1.txt"];    NSLog (@ "Len3 =%lu", [arr Count]); }

void    Mutablearraytest () {Nsmutablearray *array = [Nsmutablearray arraywithcapacity:3];    [Array addobject:@ "one"];    [Array addobject:@ ""];    [Array addobject:@ "three"];        [Array addobject:@ "TWO1"];    NSLog (@ "len =%lu", [array Count]);    [Array Removeobjectatindex:3];        NSLog (@ "len =%lu", [array Count]);    Nsenumerator *e = [array objectenumerator];    NSString *x;    while (x = [E Nextobject]) {NSLog (@ "x = =%@", x); } nsenumerator *e1 = [array reverseobjectenumerator];} 

void Dicttest () {    nsdictionary *dict = [nsdictionary dictionarywithobjectsandkeys:@ "value1", @ "Key1", @ "value2", @ " Key2 ", nil];    NSLog (@ "%@", [dict objectforkey:@ "Key2"]);        Nsmutabledictionary *d = [Nsmutabledictionary dictionarywithcapacity:3];        [D setobject:@ "wwwwww" forkey:@ "Key1"];    [D removeobjectforkey:@ "Key1"];    NSLog (@ "%lu, key1=%@", [D Count], [D objectforkey:@ "Key1"]);}

Nsarray: An ordered set of elements in an entire block of memory and arranged sequentially;

Nsset: Unordered collection, hash store.
Read Developer.apple's explanation of Nsset: You can use sets as a alternative to arrays when the order of elements isn ' t important and per Formance in testing whether an object was contained in the set is a consideration-while arrays be ordered, testing for MEM Bership is slower than with sets.
Searching for an element, Nsset is more efficient than nsarray. Why is it? The principle is simple: the storage and access of elements in Nsset is a hash process. For example, if you want to store element A, a hash algorithm can directly find the location where a should be stored, and also, when you want to access a, a hash process can find the location of a storage. For Nsarray, if you want to know if a is not in the array, you need an element comparison, obviously inefficient.

4.NSString

void stringtest () {NSString *str = [NSString stringwithformat:@ "AA,    BB,CC, "];    Nsarray *array = [str componentsseparatedbystring:@ ","];        NSLog (@ "len =%lu", [array Count]);
NSLog (@ "%@", [Array componentsjoinedbystring:@ "-"]);}