Basic use of iOS database

Last Update:2015-08-25 Source: Internet

Author: User

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today summarizes the basic use of the database method: The database used by iOS is generally sqlite3, You must first import the database framework before using the database, or you will get an error, then introduce the header file #import <sqlite3.h> Create a model class student in the project, a database tool class DatabasetoolDefine several properties in Student.h:#import <Foundation/Foundation.h>@interface Student:nsobject@property (nonatomic,copy) NSString *name;@property (nonatomic,copy) NSString *hobby;@property (nonatomic,assign) Nsinteger age;@endDeclaration of the database operation method in DataBaseTool.h: #import <Foundation/Foundation.h>#import <sqlite3.h>#import "Student.h"@interface Databasetool:nsobject{The address used to hold the database objectSqlite3 *dbpoint;}To ensure that the current database is unique in the project, we create a database tool object in a single-instance way+ (databasetool *) sharedatabasetool;Open Database-(void) opendb;Create a table for the database, table-(void) createtable;Insert a student information-(void) insertstu: (Student *) stu;Update a Student's information-(void) updatestu: (Student *) stu;Delete operation-(void) deletedatestu: (Student *) stu;Query operations-(nsmutablearray *) selectallstu;Close the database-(void) closedb;@endDATABASETOOL.M in the implementation method:#import "dataBaseTool.h"@implementation Databasetool+ (databasetool *) sharedatabasetool{Static Databasetool *tool;Static dispatch_once_t onetoken;Dispatch_once (&onetoken, ^{Tool=[[databasetool alloc] init];});Return tool;}-(void) opendb{The database file is also stored in the sandbox documents file, so find the sandbox path firstNsarray *sandbox=nssearchpathfordirectoriesindomains (nsdocumentdirectory, nsuserdomainmask, YES);NSString *sandboxpath=sandbox[0];Stitching the file path, if the system according to the file path to find the corresponding file will open the database directly, if not it will create a corresponding databaseNSString *documentpath=[sandboxpath stringbyappendingpathcomponent:@ "student.sqlite"];int Result=sqlite3_open ([documentpath utf8string], &dbpoint);If (result==sqlite_ok) {NSLog (@ "database Open successfully");NSLog (@ "%@", documentpath);}else{NSLog (@ "database Open failed");}}-(void) createtable{Primary key is the primary key meaning, the main living table data is unique, cannot be duplicated, can uniquely identify a piece of data, is generally an integerAutoIncrement self-increment, in order to let the primary key does not repeat, will let the primary key adopt the Self-increment wayIf not exists if no table is created, prevents duplicate creation before overwriting dataDatabase problem 90% is a SQL statement problem, so ensure that the statement is not a problem, and then put in the project to useNSString *[email protected] "create table if not exists Stu (number integer primary key autoincrement,name text,age integer , Hobby Text) ";Execute this SQL statementint result=sqlite3_exec (dbpoint, [sqlstr utf8string], nil, nil, nil);If (result==sqlite_ok) {NSLog (@ "table Creation succeeded");}else{NSLog (@ "table Creation failed");}}-(void) insertstu: (Student *) stu{NSString *sqlstr=[nsstring stringwithformat:@ "insert into Stu (name,age,hobby) values ('%@ ', '%ld ', '%@ ')", stu.name, Stu.age,stu.hobby];Execute SQL statementint result=sqlite3_exec (dbpoint, [sqlstr utf8string], nil, nil, nil);If (result==sqlite_ok) {NSLog (@ "add Student success");}else {NSLog (@ "add Student failed");}}-(void) updatestu: (Student *) stu{NSString *sqlstr= [nsstring stringwithformat:@ "update Stu set hobby= '%@ ', age=%ld where name= '%@ '", stu.hobby,stu.age, stu.name];Execute SQL statementint result=sqlite3_exec (dbpoint, [sqlstr utf8string], nil, nil, nil);If (result==sqlite_ok) {NSLog (@ "update succeeded");}else{NSLog (@ "update failed");NSLog (@ "%d", result);}}-(void) deletedatestu: (Student *) stu{NSString *sqlstr=[nsstring stringwithformat:@ "delete from Stu where name= '%@ '", stu.name];Execute SQL statementint result=sqlite3_exec (dbpoint, [sqlstr utf8string], nil, nil, nil);If (result==sqlite_ok) {NSLog (@ "delete succeeded");}else{NSLog (@ "delete failed");}}-(nsmutablearray *) selectallstu{Query logic1. First read all data from a table in a local database2. Then read by article, assign the model to the value3. Put the already assigned model into the array and returnNSString *[email protected] "select * from stu";In the statement * is a wildcard meaning, through a * equivalent to replace all the field names in the tablenext, you need to define a follow pointer that iterates through each row of data in the database Table.Third Parameter: query statement word limit, 1 is no limitSqlite3_stmt *stmt=nil;int result=sqlite3_prepare_v2 (dbpoint, [sqlstr utf8string],-1, &stmt, nil);This method is equivalent to associating the database with the following pointers and completing the query function together.Initialize an array to fit the studentNsmutablearray *stuarr=[nsmutablearray array];If (result==sqlite_ok) {NSLog (@ "query success");Start traversing every row of data in the query databaseWhile (sqlite3_step (stmt) ==sqlite_row) {Let the follow pointer traverse the query and stop the loop if there are no rowsIf the condition is met, the column-wise read contentThe second parameter represents the current column of data in the first column of the tableConst unsigned char *name=sqlite3_column_text (stmt, 1);int Age=sqlite3_column_int (stmt, 2);Const unsigned char *hobby=sqlite3_column_text (stmt,3);Convert joins data to typeNsinteger stuage=age;NSString *stuname=[nsstring stringwithutf8string: (const Char *) name];NSString *stuhobby=[nsstring stringwithutf8string: (const Char *) hobby];Assigns a value to an object and then places the object in an arrayStudent *stu=[[student alloc] init];stu.name=stuname;stu.hobby=stuhobby;stu.age=stuage;[stuarr addobject:stu];[stu release];}}else{NSLog (@ "query failed");NSLog (@ "%d", result);}Return stuarr;}-(void) closedb{ int Result=sqlite3_close (dbpoint);If (result==sqlite_ok) {NSLog (@ "database shutdown succeeded");NSLog (@ "%@", documentpath);}else{NSLog (@ "database shutdown failed");}}@endBasic use of iOS database

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